At the moment i use radeon ddx from git (older snapshot) with dri3.
Most apps work, but for example

DRI_PRIME=1 kodi

let freeze the whole xserver and let a zombie process left for /usr/bin/X.

Working over ssh still working. But reboot or halt is not possible, only hard
switch off.

I will try to use a new git snapshot and will tell, what's going on with it.