Found this thread while googling the error from the log.

AMD Ryzen 3600
Asrock B350 motherboard
ASrock RX560 Radeon GPU

Ubuntu and Xubuntu  18.04 and 19.04 both lockups so not useable, after login
almost imminent black screen, ssh access still possible. Seems a newer kernel
and mesa drivers. sometimes 5 min , sometimes after 2 secomds

Linux mint 19.2
Seems a lot more stable but so far only  1 lockup with black screen

uname -a
Linux jeroenimo-amd 4.15.0-64-generic #73-Ubuntu SMP Thu Sep 12 13:16:13 UTC
2019 x86_64 x86_64 x86_64 GNU/Linux

Last log from mint:

Sep 25 23:01:57 jeroenimo-amd kernel: [ 4980.207322]
[drm:drm_atomic_helper_wait_for_flip_done [drm_kms_helper]] *ERROR*
[CRTC:43:crtc-0] flip_done timed out
Sep 25 23:01:57 jeroenimo-amd kernel: [ 4980.207331]
[drm:drm_atomic_helper_wait_for_flip_done [drm_kms_helper]] *ERROR*
[CRTC:45:crtc-1] flip_done timed out
Sep 25 23:02:07 jeroenimo-amd kernel: [ 4990.451366]
[drm:drm_atomic_helper_wait_for_dependencies [drm_kms_helper]] *ERROR*
[CRTC:43:crtc-0] flip_done timed out

 I suspect I'm in the same trouble as most.

Win 10 flawless so it's really software..