intel graphics not loading on old kernel

I have a Linux Ubuntu 20.04 system in a clean room, which I use for testing a scientific camera for a stratospheric telescope mission. The problem I am facing is that the drivers of the frame grabber card that I use with the camera are not compatible with kernels 5.8.0-x. I did not know it at first and I updated the system two months ago by mistake to fix another issue. When I figured out that I could not build the frame grabber drivers again, I kept using the old 5.4.0-58 kernel that was still installed on system and available in grub and it worked fine up to today.

Today I came back to the lab and saw that the 5.4.0-58 kernel is removed from grub by unattended-upgrade process yesterday (based on log).

I reinstalled the kernel I needed, but now unfortunately the graphic drivers are somehow not loading. The newer kernel versions work still fine. But there are no active graphic drivers when I boot in the old kernel version. might it be that the graphic drivers are somehow updated and are not compatible with the old kernel anymore? Is there a way to roll back a specific driver? and how should I know which Intel driver to use for this specific kernel?

I have the following graphic drivers:
```
00:02.0 VGA compatible controller: Intel Corporation 4 Series Chipset Integrated Graphics Controller (rev 03)
00:02.1 Display controller: Intel Corporation 4 Series Chipset Integrated Graphics Controller (rev 03)
```
and when using kernel 5.4.0-58
```
 lshw -c video
```
returns:
```
  *-display:0 UNCLAIMED
       description: VGA compatible controller
       product: 4 Series Chipset Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 03
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list
       configuration: latency=0
       resources: memory:f0000000-f03fffff memory:e0000000-efffffff ioport:1230(size=8) memory:c0000-dffff
  *-display:1 UNCLAIMED
       description: Display controller
       product: 4 Series Chipset Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2.1
       bus info: pci@0000:00:02.1
       version: 03
       width: 64 bits
       clock: 33MHz
       capabilities: pm bus_master cap_list
       configuration: latency=0
       resources: memory:f0400000-f04fffff
```
while on other kernels (I have 5.8.0-41 and 5.8.0-43), it reports:
```
*-display:0
       description: VGA compatible controller
       product: 4 Series Chipset Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 03
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:16 memory:f0000000-f03fffff memory:e0000000-efffffff ioport:1230(size=8) memory:c0000-dffff
  *-display:1 UNCLAIMED
       description: Display controller
       product: 4 Series Chipset Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2.1
       bus info: pci@0000:00:02.1
       version: 03
       width: 64 bits
       clock: 33MHz
       capabilities: pm bus_master cap_list
       configuration: latency=0
       resources: memory:f0400000-f04fffff
```
Also in system details on kernel 5.4.0-58 the graphics is mentioned as
llvmpipe (LLVM 11.0.0, 128 bits), but it should be Intel® Q45/Q43 (ELK)

I did try editing the grub file with recommendations from the other posts, but it did not solve the issue.

I am not that knowledgeable in these topics and I am not a trained software engineer. So if my questions are very basic, I am sorry.I theoretically can start from scratch and install Ubuntu again with the kernel I need, but I have alot of libraries built on this system, which took me a full week last time. I would very much like to avoid it if possible.

So right now I would like to know why the driver stopped loading after reinstalling the kernel, eventhough it was working a day before quite fine...and how can I fix the intel driver issue for this exact kernel that I need?

Thank you very much