Dell XPS 9550 Boots Won't Boot To Ubuntu 20.04 After Upgrade from GUI; Windows Partition Boots Fine

Make sure fast boot is off in windows. https://i.stack.imgur.com/TEJgH.png then restart to see if the grub boot loader starts.
 https://askubuntu.com/questions/1031993/how-to-install-ubuntu-18-04-alongside-windows-10
Should be able to turn fast boot off in the Bios.
To collect debugging information open terminal and type: ubuntu-bug linux
Apport will start to collect information. https://wiki.ubuntu.com/Apport

Thanks for your help! Fast boot is still off; I'm pretty sure I disabled when I originally installed 18.04, so I wouldn't expect it have been reenabled after upgrading to 20.04 (although it was worthwhile to double check).

Regarding the debugging information-- since I can't actually load into my Ubuntu install, I can't activate Apport, correct? Or is there some way to do this from grub?

Have you tried selecting an older kernel version from the grub menu, and does this show the same problem?

Since you have the nVidia graphics card, you may want to try temporarily disabling both types of nVidia driver from Grub and rely on your Intel i915 only. This is where the screens attach, so you should get an image without them. You would need to add:
module_blacklist=nouveau,nvidia

If that allows you to boot, it will then allow uploading of support information the normal way.

Thanks again all for your continued assistance:

@m-hampl - I have tried selectin an older kernel version from the grub menu; loading recovery mode with 4.15.0-118-generic yields the same result (Freezes at 'Loading initial ramdisk...')

@tonyvroon - this advice yielded some interesting results. If I added `module_blacklist=nouveau,nvidia` when trying to load from an Ubuntu 20.04 installation USB in UEFI mode, I *was* able to boot into Ubuntu from the live pendrive (something that I was previously unable to do). However, I tried doing adding this same line in recovery mode for the Ubuntu on my actual machine, and the freezing on "Loading initial ramdisk" symptom remains. I'm not sure what to do with this information... Please let me know if there is more information I can provide-- I took a few photos of my screen while I was troubleshooting using your direction- I can upload if you feel it would be helpful.

Please could you try on your actual machine:
dis_ucode_ldr module_blacklist=nouveau,nvidia

If that allows you to boot, please then try to update all packages, paying particular attention to anything kernel, ucode & microcode.

Thank you, Tony-- I tried running `dis_ucode_ldr module_blacklist=nouveau,nvidia` on my actual machine, and only got a black screen. I also tried adding `module_blacklist=nouveau,nvidia` in recovery mode (`dis_ucode_ldr` was already present) and it once again froze at "Loading initial ramdisk..."

Provided you don't use bitlocker on your Windows 10 installation... could you check if you have a "PTT security" option in your BIOS, and if so, turn it off. This is a software-emulated TPM that may be upsetting things. If you do have BitLocker enabled, changing anything TPM-related could endanger your data, so please check that first.

Thanks-- I don't believe I have Bitlocker to my knowledge, and this is Windows Home Edition so I believe it is not an available feature. I do not have a PTT entry that I see in my BIOS, but I *do* have a TPM entry. It is currently turned on but disabled-- I believe this state is where I left it in my last round of testing on trying to get my Ubuntu install up and running again. I'll admit I don't really have much of an understanding of what TPM is doing-- I was mostly just trying to troubleshoot. I took a photo of the TPM BIOS screen and uploaded it to imgur here: https://imgur.com/qaNGFTB

Could you try with:
earlyprintk=vga,keep module_blacklist=nouveau,nvidia

This will appear in a strange font and will not be pretty, but it may give a better idea of kernel state when the system hangs. If you get useful text output to this, please attach a photograph.

Thanks for sticking with me on this problem. Unfortunately, that didn't yield anything. I tried adding it in the regular boot, the recovery boot for kernel v5 and kernel v4, and had the same exact result for all three. You can see [here](https://imgur.com/a/ou0TXFr) where I added it to the linux line for the v4 kernel, and the output. I waited about five minutes before I gave up.

FWIW, I didn't note it before but my machine has a 4k screen. I thought it would be an unimportant detail, but as I was researching my slow input time on GNU GRUB I found this post on AskUbuntu that notes it is an issue for 4K screens (which the 9550 has): https://askubuntu.com/questions/1227735/grub-is-extremely-slow-1-second-per-key-input

I still assume that it has no bearing on the issue being discussed here, but figured I'd raise it just in case.

@TonyVroon:
Also: At this juncture, since you've got me to the point where I can load the installer, would it make sense to try to leverage [Boot-Repair](https://help.ubuntu.com/community/Boot-Repair). Or is that unlikely to resolve any issues for me?

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

Sorry to reopen, but I'll take any advice anyone is willing to provide. I'd prefer to avoid having to do a full reinstall. My assumption was a standard upgrade from one LTS to another LTS shouldn't brick the OS-- is there something I should do differently in the future?

Thanks.

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