duncan: thanks, that was it.

IME Linux will work just fine without doing that (I've been using coreboot + kexecboot/petitboot for a while), it seems to do its own init of the hardware

Not so much with BSD and others, and it's really annoying trying to work it out as there usually aren't any error messages apparent

E.g. on FreeBSD X11 will not find the intel video driver despite i915kms loading and setting the correct resolution, and Wayland will work fine with 3D acceleration