An update:
Coinciding with OpenBSD6.6-current, the amdgpu code is enabled by default - no need to build a custom kernel.
Based on the Arch Linux wiki:
https://wiki.archlinux.org/index.php/AMDGPU
I tried some different settings.
The following /etc/X11/xorg-conf.d/20-amdgpu.conf:
Code:
Section "Device"
Identifier "2200G"
Driver "amdgpu"
Option "SWCursor" "on"
Option "TearFree" "on"
EndSection
Provides a well-behaved mouse pointer.
This looks to be ready to be my main work station when 6.6 is released