Failure to build Ubuntu Groovy Kernel 5.8.0-43 low latency

The version number string seems wrong to me

The build looks for
418.181.07-0ubuntu0~0.20.10.0.1
but the Ubuntu repositories have
418.181.07-0ubuntu0.20.10.1

Tried this again using the sources from

$ apt-get source linux-image-unsigned-$(uname -r)
$ cd linux-5.8.0

and build with

$ LANG=C fakeroot debian/rules binary

This seems to get the correct 418.181.07-0ubuntu0~0.20.10.0.1
It looks that the git repository is not correct ?

That failed with :

error: 'nvidia-kernel-source-418-server_418.181.07-0ubuntu0.20.10.1_amd64.deb' is not a Debian format archive

====
II: dkms-build downloading nvidia-418srv (nvidia-kernel-source-418-server_418.181.07-0ubuntu0.20.10.1_amd64.deb)
II: fetching https://launchpad.net/ubuntu/+archive/primary/+files/nvidia-kernel-source-418-server_418.181.07-0ubuntu0.20.10.1_amd64.deb
II: fixing https://launchpadlibrarian.net/518369473/nvidia-kernel-source-418-server_418.181.07-0ubuntu0.20.10.1_amd64.deb
II: following http://launchpadlibrarian.net/518369473/nvidia-kernel-source-418-server_418.181.07-0ubuntu0.20.10.1_amd64.deb
curl: (7) Couldn't connect to server
dpkg-deb: error: 'nvidia-kernel-source-418-server_418.181.07-0ubuntu0.20.10.1_amd64.deb' is not a Debian format archive
make: *** [debian/rules.d/2-binary-arch.mk:229: install-lowlatency] Error 2
====

I checked and the /deb url does exist.

Removed linux-5.8.0/debian/linux-modules-extra-5.8.0-43-generic/lib/modules/5.8.0-43-generic/kernel/kernel

and restarted the build, then got

make[3]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[3]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
[ -x ./scripts/zfs-tests.sh ] && \
    ./scripts/zfs-tests.sh -c
make[3]: [Makefile:1535: all-local] Error 1 (ignored)
make[3]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make[2]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make[1]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make: *** [debian/rules.d/2-binary-arch.mk:223: install-generic] Error 1

Thus still no succes.

curl: (7) Couldn't connect to server
dpkg-deb: error: 'nvidia-kernel-source-418-server_418.181.07-0ubuntu0.20.10.1_amd64.deb' is not a Debian format archive

This looks like a download problem.

Started all over once again from scratch

1 Deleted all Linux sources apt-get source linux-image-unsigned-$(uname -r)
2. Downloaded the kernel source again,
3 Followed al the steps at https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel
4. Got the exact same error "could not connect to to server"
5 Removed the linux folder
     linux-5.8.0/debian/linux-modules-extra-5.8.0-43-generic/lib/modules/5.8.0-43-generic/kernel/kernel
6. Restarted the build LANG=C fakeroot debian/rules binary
7. Same error

make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
make[4]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
make[4]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[4]: Nothing to be done for 'all-am'.
make[4]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[3]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[3]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
[ -x ./scripts/zfs-tests.sh ] && \
    ./scripts/zfs-tests.sh -c
make[3]: [Makefile:1535: all-local] Error 1 (ignored)
make[3]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make[2]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make[1]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make: *** [debian/rules.d/2-binary-arch.mk:223: install-generic] Error 1
make: *** [debian/rules.d/2-binary-arch.mk:223: install-generic] Error 1

That can't be coincidence.
The line 223 in 2-binary-arch.mk shows

222 /sbin/depmod -b $(pkgdir) -ea -F $(pkgdir)/boot/System.map-$(abi_release)-$* \
223 $(abi_release)-$* 2>&1 |tee $(target_flavour).depmod.log; \

Now stuck here.

In the title of the question you talk about
"Groovy Kernel 5.8.0-41"
but in your last comment you tell
"Removed ... linux-modules-extra-5.8.0-43-generic ..."

Is this a typo error?

Is there any useful information in the build log or dkms log files?

When I pulled apt-get source linux-image-unsigned-$(uname -r) today it retrieved 5.8.0-43-generic
it seem my Ubuntu version is also at kernel 5.8.0-43-generic now.
uname -a
Linux H3U1 5.8.0-43-lowlatency #49-Ubuntu SMP PREEMPT Fri Feb 5 04:42:29 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

Is there any useful information in the build log or dkms log files?

Where are those log files stored ? Looked around in the tree and search the internet but can't find hints where to look.
Don't see anything related in /var/logs

Changed the subject name

Gave up the git sources because of the nvidia- kernel-sources issue.
Continued with the apt-get source linux-image-unsigned-$(uname -r)

With this the generic kernel (LANG=C fakeroot debian/rules binary-headers binary-generic binary-perarch builds) succeeds.

The low latency kernel (LANG=C fakeroot debian/rules binary) fails., and root contents after the failure is:

drwxrwxr-x 27 user user 4096 Feb 19 15:39 linux-5.8.0
-rw-r--r-- 1 user user 3616779 Feb 6 06:14 linux_5.8.0-43.49.diff.gz
-rw-r--r-- 1 user user 8529 Feb 6 06:14 linux_5.8.0-43.49.dsc
-rw-r--r-- 1 user user 178322327 Aug 12 2020 linux_5.8.0.orig.tar.gz
-rw-r--r-- 1 user user 243604 Feb 19 15:39 linux-cloud-tools-5.8.0-43_5.8.0-43.49_amd64.deb
-rw-r--r-- 1 user user 233000 Feb 19 15:39 linux-cloud-tools-common_5.8.0-43.49_all.deb
-rw-r--r-- 1 user user 9931912 Feb 19 15:39 linux-doc_5.8.0-43.49_all.deb
-rw-r--r-- 1 user user 11538176 Feb 19 15:39 linux-headers-5.8.0-43_5.8.0-43.49_all.deb
-rw-r--r-- 1 user user 225916 Feb 19 15:38 linux-source-5.8.0_5.8.0-43.49_all.deb
-rw-r--r-- 1 user user 6049628 Feb 19 15:39 linux-tools-5.8.0-43_5.8.0-43.49_amd64.deb
-rw-r--r-- 1 user user 410276 Feb 19 15:39 linux-tools-common_5.8.0-43.49_all.deb
-rw-r--r-- 1 user user 241984 Feb 19 15:39 linux-tools-host_5.8.0-43.49_all.deb

Last outputs lines:

  LD [M] drivers/net/ethernet/mellanox/mlxsw/mlxsw_minimal.o
make[5]: *** [/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/scripts/Makefile.build:519: drivers/net/ethernet/mellanox] Error
make[5]: *** Waiting for unfinished jobs....
  CC [M] drivers/net/ethernet/qlogic/qed/qed_fcoe.o
  CC [M] drivers/net/ethernet/qlogic/qed/qed_ooo.o
  LD [M] drivers/net/ethernet/qlogic/qed/qed.o
make[4]: *** [/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/scripts/Makefile.build:519: drivers/net/ethernet] Error 2
make[3]: *** [/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/scripts/Makefile.build:519: drivers/net] Error 2
make[2]: *** [/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/Makefile:1780: drivers] Error 2
make[2]: Leaving directory '/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/debian/build/build-generic'
make[1]: *** [Makefile:185: __sub-make] Error 2
make[1]: Leaving directory '/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0'
make: *** [debian/rules.d/2-binary-arch.mk:50: /media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/debian/stamps/stamp-build-generic] Error 2

I found the following for low latency kernel., this isn't mentioned on ubuntu wiki:
https://ahelpme.com/linux/ubuntu/build-your-own-kernel-under-ubuntu-using-mainline-latest-kernel/
There are two external dependency libraries SPL and ZFS – you must download them and put them in the sub-directory to the main v4.17.19 –

But not sure yet how to get these.

Got one successfull low latency build.
After a clean to regress this keep bumping into

CC [M] drivers/net/net_failover.o
  AR drivers/net/built-in.a
  LD [M] drivers/net/thunderbolt-net.o
make[2]: *** [/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/Makefile:1780: drivers] Error 2
make[2]: Leaving directory '/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/debian/build/build-generic'
make[1]: *** [Makefile:185: __sub-make] Error 2
make[1]: Leaving directory '/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0'
make: *** [debian/rules.d/2-binary-arch.mk:50: /media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/debian/stamps/stamp-build-generic] Error 2

I assume the important message that might help finding the root cause is further up.
Please provide more lines of output.

Addeds to the kernel tree and checked out version0.8.4 as discussed here
https://forum.level1techs.com/t/building-custom-kernel-with-zfs-built-in-updated-0-8-or-higher/142000

It still fails.

make[3]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
[ -x ./scripts/zfs-tests.sh ] && \
    ./scripts/zfs-tests.sh -c

* Where is DKMSDIR ?
* Where can I find the build log or dkms log files?

it seems very difficult to compile a ubuntu 20.10 low latecy kernel
For example wiki says sudo apt-get build-dep linux linux-image-$(uname -r)
that won't work for uname- a it result in Linux H3U1 5.8.0-43-lowlatency and getting sourcew won't work

Picking 'linux-signed' as source package instead of 'linux-image-5.8.0-43-lowlatency'
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

So I used # sudo apt-get source linux-image-unsigned-$(uname -r)
but with that, restarting from scratch, Getting random segementtion errors example

/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/include/net/sock.h: In function 'sock_flag':
/media/user/H3D1P2/Tools/kernel_apt/linux-5.8.0/include/net/sock.h:883:20: internal compiler error: Segmentation fault
  883 | static inline bool sock_flag(const struct sock *sk, enum sock_flags flag)
      | ^~~~~~~~~
Please submit a full bug report

Ok, starting clean again. here are steps

apt-get source linux-image-unsigned-$(uname -r)
cd linux-5.8.0
chmod a+x debian/rules
chmod a+x debian/scripts/*
chmod a+x debian/scripts/misc/*
LANG=C fakeroot debian/rules clean
LANG=C fakeroot debian/rules editconfigs
LANG=C fakeroot debian/rules binary

Why arethese segmentation erros happening ? Should I use another compiler version ?

gcc (Ubuntu 10.2.0-13ubuntu1) 10.2.0

media/user/H3D2P1/kernel/linux-5.8.0/drivers/gpu/drm/nouveau/nvkm/engine/disp/rootnv50.c:361:1: internal compiler error: Segmentation fault
  361 | };
      | ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <file:///usr/share/doc/gcc-10/README.Bugs> for instructions.
make[6]: *** [/media/user/H3D2P1/kernel/linux-5.8.0/scripts/Makefile.build:290: drivers/gpu/drm/nouveau/nvkm/engine/disp/rootnv50.o] Error 1
make[6]: *** Waiting for unfinished jobs....
  CC [M] drivers/gpu/drm/gma500/gma_display.o
  CC [M] drivers/gpu/drm/gma500/gma_device.o
make[5]: *** [/media/user/H3D2P1/kernel/linux-5.8.0/scripts/Makefile.build:519: drivers/gpu/drm/nouveau] Error 2
make[5]: *** Waiting for unfinished jobs....
  CC [M] drivers/gpu/drm/gma500/psb_intel_display.o
  CC [M] drivers/gpu/drm/gma500/psb_intel_lvds.o
  CC [M] drivers/gpu/drm/gma500/psb_intel_modes.o
  CC [M] drivers/gpu/drm/gma500/psb_intel_sdvo.o
  CC [M] drivers/gpu/drm/gma500/psb_lid.o
  CC [M] drivers/gpu/drm/gma500/psb_irq.o
  CC [M] drivers/gpu/drm/gma500/psb_device.o
  CC [M] drivers/gpu/drm/gma500/mid_bios.o
  CC [M] drivers/gpu/drm/gma500/opregion.o
  CC [M] drivers/gpu/drm/gma500/cdv_device.o
  CC [M] drivers/gpu/drm/gma500/cdv_intel_crt.o
  CC [M] drivers/gpu/drm/gma500/cdv_intel_display.o
  CC [M] drivers/gpu/drm/gma500/cdv_intel_hdmi.o
  CC [M] drivers/gpu/drm/gma500/cdv_intel_lvds.o
  CC [M] drivers/gpu/drm/gma500/cdv_intel_dp.o
  CC [M] drivers/gpu/drm/gma500/oaktrail_device.o
  CC [M] drivers/gpu/drm/gma500/oaktrail_crtc.o
  CC [M] drivers/gpu/drm/gma500/oaktrail_lvds.o
  CC [M] drivers/gpu/drm/gma500/oaktrail_lvds_i2c.o
  CC [M] drivers/gpu/drm/gma500/oaktrail_hdmi.o
  CC [M] drivers/gpu/drm/gma500/oaktrail_hdmi_i2c.o
  LD [M] drivers/gpu/drm/gma500/gma500_gfx.o
make[4]: *** [/media/user/H3D2P1/kernel/linux-5.8.0/scripts/Makefile.build:519: drivers/gpu/drm] Error 2
make[3]: *** [/media/user/H3D2P1/kernel/linux-5.8.0/scripts/Makefile.build:519: drivers/gpu] Error 2
make[2]: *** [/media/user/H3D2P1/kernel/linux-5.8.0/Makefile:1780: drivers] Error 2
make[2]: Leaving directory '/media/user/H3D2P1/kernel/linux-5.8.0/debian/build/build-generic'
make[1]: *** [Makefile:185: __sub-make] Error 2
make[1]: Leaving directory '/media/user/H3D2P1/kernel/linux-5.8.0'
make: *** [debian/rules.d/2-binary-arch.mk:50: /media/user/H3D2P1/kernel/linux-5.8.0/debian/stamps/stamp-build-generic] Error 2

Just keep restarting with the same command everytime nump into

make[3]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
[ -x ./scripts/zfs-tests.sh ] && \
    ./scripts/zfs-tests.sh -c
make[3]: [Makefile:1535: all-local] Error 1 (ignored)
make[3]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make[2]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make[1]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
make: *** [debian/rules.d/2-binary-arch.mk:223: install-generic] Error 1

then an error occurs that

/linux-5.8.0/debian/linux-modules-extra-5.8.0-43-generic/lib/modules/5.8.0-43-generic/kernel

is not empty. then delete this folder restart again and then the zfs error happens again. repteat, repeat..

I do not really understad. This is the latest ubuntu 20.10 version with the latest kernel version and it can;'t be built ?
if anyone would be so kind to just repease the above steps at #13 ?

 there is last part of the output, I have no ideas anymore how to build the kow latency kernel.

  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/sa.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/sha256.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/skein_zfs.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/spa.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/spa_boot.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/spa_checkpoint.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/spa_config.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/spa_errlog.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/spa_history.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/spa_misc.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/spa_stats.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/space_map.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/space_reftree.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/txg.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/trace.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/uberblock.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/unique.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_disk.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_cache.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_file.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_indirect.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_indirect_births.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_indirect_mapping.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_initialize.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_label.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_mirror.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_missing.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_queue.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_raidz.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_raidz_math.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_raidz_math_scalar.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_removal.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_root.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_trim.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zap.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zap_leaf.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zap_micro.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zcp.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zcp_get.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zcp_global.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zcp_iter.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zcp_synctask.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfeature.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_acl.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_byteswap.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_ctldir.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_debug.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_dir.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_fm.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_fuid.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_ioctl.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_log.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_onexit.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_ratelimit.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_replay.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_rlock.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_sa.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_sysfs.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_vfsops.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_vnops.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs_znode.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zil.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zio.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zio_checksum.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zio_compress.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zio_crypt.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zio_inject.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zle.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zpl_ctldir.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zpl_export.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zpl_file.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zpl_inode.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zpl_super.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zpl_xattr.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zrlock.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zthr.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zvol.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/dsl_destroy.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/dsl_userhold.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/qat.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/qat_compress.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/qat_crypt.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_raidz_math_sse2.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_raidz_math_ssse3.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_raidz_math_avx2.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_raidz_math_avx512f.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/vdev_raidz_math_avx512bw.o
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs.o
  MODPOST <<DKMSDIR>>/build/zfs/0.8.4/build/module/Module.symvers
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/avl/zavl.mod.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/icp/icp.mod.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/lua/zlua.mod.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/nvpair/znvpair.mod.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/spl/spl.mod.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/unicode/zunicode.mod.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zcommon/zcommon.mod.o
  CC [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs.mod.o
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/avl/zavl.ko
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/icp/icp.ko
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/lua/zlua.ko
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/nvpair/znvpair.ko
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/spl/spl.ko
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/unicode/zunicode.ko
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zcommon/zcommon.ko
  LD [M] <<DKMSDIR>>/build/zfs/0.8.4/build/module/zfs/zfs.ko
make[4]: Leaving directory '<<DKMSDIR>>/headers/linux-headers-5.8.0-43-generic'
make[3]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/module'
Making all in include
make[3]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
Making all in linux
make[4]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/linux'
make[4]: Nothing to be done for 'all'.
make[4]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/linux'
Making all in spl
make[4]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/spl'
Making all in rpc
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/spl/rpc'
make[5]: Nothing to be done for 'all'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/spl/rpc'
Making all in sys
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/spl/sys'
make[5]: Nothing to be done for 'all'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/spl/sys'
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/spl'
make[5]: Nothing to be done for 'all-am'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/spl'
make[4]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/spl'
Making all in sys
make[4]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
Making all in fm
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/fm'
Making all in fs
make[6]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/fm/fs'
make[6]: Nothing to be done for 'all'.
make[6]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/fm/fs'
make[6]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/fm'
make[6]: Nothing to be done for 'all-am'.
make[6]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/fm'
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/fm'
Making all in fs
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/fs'
make[5]: Nothing to be done for 'all'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/fs'
Making all in crypto
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/crypto'
make[5]: Nothing to be done for 'all'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/crypto'
Making all in lua
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/lua'
make[5]: Nothing to be done for 'all'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/lua'
Making all in sysevent
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/sysevent'
make[5]: Nothing to be done for 'all'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/sysevent'
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
make[5]: Nothing to be done for 'all-am'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
make[4]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
make[4]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[4]: Nothing to be done for 'all-am'.
make[4]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[3]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[3]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
[ -x ./scripts/zfs-tests.sh ] && \
    ./scripts/zfs-tests.sh -c
make[3]: [Makefile:1535: all-local] Error 1 (ignored)

Before digging into further details, some basic questions:

What exactly do you want to achieve?
The 5.8.0-43-lowlatency kernel for groovy is available in the Ubuntu repositories, so why do you want to compile yourself?

And messages like

media/user/H3D2P1/kernel/linux-5.8.0/drivers/gpu/drm/nouveau/nvkm/engine/disp/rootnv50.c:361:1: internal compiler error: Segmentation fault
  361 | };
      | ^
Please submit a full bug report,

indicate that something totally unexpected happened. You should consider reporting a bug report as requested.

I now installed the same ubuntu version in a KVM with 12GB memory and 4 CPU to see if that giavce the same resut/
It did and at the exact same point getting stuck. This also happened after a segmentation fault and restarting the build.
That can't be coincidence.

make[5]: Nothing to be done for 'all'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys/sysevent'
make[5]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
make[5]: Nothing to be done for 'all-am'.
make[5]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
make[4]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include/sys'
make[4]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[4]: Nothing to be done for 'all-am'.
make[4]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[3]: Leaving directory '<<DKMSDIR>>/build/zfs/0.8.4/build/include'
make[3]: Entering directory '<<DKMSDIR>>/build/zfs/0.8.4/build'
[ -x ./scripts/zfs-tests.sh ] && \
    ./scripts/zfs-tests.sh -c

I wanted to change a kernel (ALSA) kernel module and could not find direction on how to do that.
I that I have found how to compile a kernel modules without having to compile the whole kernel.
Though, itt seems the build process for low latency kernel 5.0.8.43 is broken.
Is there a reason I should not be expected to work out of the box based on instruction in the Wiki ?
The Wiki also points using "binary" as compiling it so assumed it should be easy work, but it doesn't.
That took me a week to find out.

This question was expired because it remained in the 'Open' state without activity for the last 15 days.