I sincerely hope they haven't bit more than they can chew with that one – answering requests for videos showing the ubuntu version before the campain ends (which it has) went from "we hope to be able to" to "soon™" and "well, we'll at least ship them at the same time as the others".
Some people in the comments seem to have discovered upstream support for the intel graphics, at least. But there was no answer exactly which components need new drivers, to begin with.
That said, I'd be okay with manually rotating the screen (xrandr) as people on the GPD Win have done and the accelerometer wouldn't be essential for me, as well. I'd guess most other components will be quite standard and supported anyways.