> not likely related.

Alright, any hint where to start looking? As I said before it looks like the
visual corruption (this https://pasteboard.co/qrC9mh4p.jpg) at boot starts at

[drm] amdgpu atom DIG backlight initialized
[drm] AMDGPU Display Connectors
[drm] Connector 0:
[drm]   eDP-1
[drm]   HPD1
[drm]   DDC: 0x4868 0x4868 0x4869 0x4869 0x486a 0x486a 0x486b 0x486b
[drm]   Encoders:
[drm]     LCD1: INTERNAL_UNIPHY
[drm] Connector 1:
[drm]   HDMI-A-1
[drm]   HPD2
[drm]   DDC: 0x486c 0x486c 0x486d 0x486d 0x486e 0x486e 0x486f 0x486f
[drm]   Encoders:
[drm]     DFP1: INTERNAL_UNIPHY
[drm] amdgpu atom DIG backlight initialized
[drm] AMDGPU Display Connectors
[drm] Connector 0:
[drm]   eDP-1
[drm]   HPD1
[drm]   DDC: 0x4868 0x4868 0x4869 0x4869 0x486a 0x486a 0x486b 0x486b
[drm]   Encoders:
[drm]     LCD1: INTERNAL_UNIPHY
[drm] Connector 1:
[drm]   HDMI-A-1
[drm]   HPD2
[drm]   DDC: 0x486c 0x486c 0x486d 0x486d 0x486e 0x486e 0x486f 0x486f
[drm]   Encoders:
[drm]     DFP1: INTERNAL_UNIPHY

Fortunately it disappears after ~2 seconds when plymouth kicks in. My
impression is that the visual corruption is triggered again when interpreting
some atombios code, not really easy to debug.