Created attachment 145518 [details]
dmesg

My system runs fine until I try to start com.valvesoftware.Steam or
org.signal.Signal via Flatpak (org.zulip.Zulip works fine).  Then the graphical
X screen locks up and does not react to input (key presses, mouse clicks)
anymore.  Moving the mouse cursor is visible.  I can move to another VT
(ctrl+alt+F2), log in and `flatpak kill ...` the offending application, switch
back to the first VT and the system is back to normal without any obvious
damage.  In dmesg I will find a bunch of messages like these:
[  204.449968] amdgpu 0000:0a:00.0: [gfxhub] retry page fault (src_id:0 ring:0
vmid:1 pasid:32770, for process X pid 2148 thread X:cs0 pid 2151)
[  204.449977] amdgpu 0000:0a:00.0:   in page starting at address
0x0000000107720000 from 27
[  204.449982] amdgpu 0000:0a:00.0: VM_L2_PROTECTION_FAULT_STATUS:0x00101031

Device 0000:0a:00.0 is an AMD Ryzen 5 2400G.