Constant freezing with Ubuntu 26.04 install with AMD integrated graphics

I am trying to install Ubuntu 26.04 on a new PC with an AMD Ryzen 7 7700X. There is no dedicated GPU so I am using the integrated graphics.

At the login screen the screen goes black every few seconds. If it is enough time to log in, the screen goes black after a few seconds and I am back at the login screen.

The recurring error is:

amdgpu 0000:11:00.0: ring gfx_0.1.0 timeout, signaled seq=15, emitted seq=16 
amdgpu 0000:11:00.0: Process gnome-shell pid 10912 thread gnome-shel:cs0 pid 10209 
amdgpu 0000:11:00.0: Starting gfx_0.1.0 ring reset 
amdgpu 0000:11:00.0: Ring gfx_0.1.0 reset failed 
amdgpu 0000:11:00.0: [drm] *ERROR* Failed to initialize parser -125!

Reading some related errors, I have tried a couple of things so far:

1. Update the BIOS

2. Run memtest -> 25 passes overnight all clear

3. Change UMA Frame Buffer size to 2GB in the BIOS

4. Tried regressing the kernel, but wasn't able to (only 7.x.x versions are listed by mainline:

   sudo mainline --install 6.12.0

   Kernel "6.12.0" not found

5. Several grub settings

   GRUB_CMDLINE_LINUX_DEFAULT="quiet splash amdgpu.gfxoff=0 amdgpu.runpm=0 pcie_aspm=off"

   GRUB_CMDLINE_LINUX_DEFAULT="quiet splash amdgpu.dcdebugmask=0x10" GRUB_CMDLINE_LINUX_DEFAULT="quiet splash amdgpu.dcfeaturemask=0x2 amdgpu.ppfeaturemask=0xfffd7fff"

6. And finally use a live USB to try Ubuntu 24.04, which also freezes immediately (no black screen but blurry display)

7. Tried DP and HDMI cables.

The only think that works is to boot into save graphics or apply GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset", but it's not a long-term solution.

Any ideas for further troubleshooting? To me the issue seems to be the integrated graphics on the CPU, but could it be anything else?

Would greatly appreicate any suggestions!