amdgpu/navi14 BOOT CRASH: memtype_reserve failed

I am using a Lenovo 3000 N200. It has an Intel GM965 gpu, its latest BIOS is from 2008.
The CPU is relatively modern (Core2 Extreme X9000), 8GB memory.

My current OS is Debian 10, very close to Ubuntu Focal, of course just apt-upgraded everything.

I want to use a Radeon RX 5500 XT as an external gpu for several tasks, connecting it up with an eGPU adaptor going into the ExpressCard slot. I tried a Nvidia Tesla before and it worked perfectly. I was able to run apps using that card. However, when I put the Radeon into the adaptor, instead of the login screen, I only see the textmode login screen.

If I enter lspci then, the card is properly listed; its display device and its audio device.
Xorg is not even starting, there is no Xorg log file present. If I unplug the pcie adaptor and reboot, everything works fine (using the integrated gpu), hotplugging the card in after boot does not do anything, lcpci list not changing.

I thought that maybe the i915 module is conflicting with amdgpu but even with that module disabled, the same issue appears. I assume that it is related to the BIOS. Attached is the full DMESG. At line 1021, the crash starts:

---
[ 6.063983] memtype_reserve failed: [mem 0x00000000-0xffffffffffffffff], req write-combining
[ 6.063992] WARNING: CPU: 1 PID: 278 at arch/x86/mm/pat/memtype.c:588 memtype_reserve+0x263/0x2b0
---

Of course, I will try and do everything you want in order to help here.
Thanks