> To summarize, we’re just missing ‘--with-video=fbdev,drm2d’ and then
> we’re done, right?

Reading the kmscon source code (configure.ac), it seems that the default
is "fbdev,drm2d,drm3d".

I suspect that the drm hangs the kernel in Florian's case.

It indeed might make sense to try whether "--with-video=fbdev,drm2d"
(i.e. without "drm3d") improves things, and if not, just disable drm
modesetting at bootup.  If it's not there then it can't break :P