Someone on this list suggested this change to me (also using i915drmkms0)
--- /etc/X11/xorg.conf 2020/04/01 20:12:03 1.1
+++ /etc/X11/xorg.conf 2020/04/01 20:16:15
@@ -75,7 +75,8 @@
#Option "DebugWait" # [<bool>]
#Option "BufferCache" # [<bool>]
Identifier "Card0"
- Driver "wsfb"
+ Driver "intel"
+ Option "AccelMethod" "uxa"
BusID "PCI:0:2:0"
EndSection
and X11 is fairly usable for me. Every now and then I see messages like
kern error: [drm:(/usr/src/sys/external/bsd/drm2/dist/drm/i915/intel_sprite.c:132)intel_pipe_update_start] *ERROR* Potential atomic update failure on pipe A: -35
but X11 is stable and I don't have any visual artefacts.