30-bit depth with Linux driver does not produce 30-bit output on monitor

ayaka, as mate is a gnome fork, it’s probably hit by the same 30bit bugs. See this for a general workaround, though that’s about mouse clicks:
[url]104808 – [mesa 18.0.0-rc2][bisected] Radeonsi doesn’t work correctly in wayland session (gnome-shell)
of course, this has to be modified for the corresponding mate processes.