Hi Alex,
I believe that the revert of "drm/radeon: only mark audio as connected if the monitor supports it (v3)" causes issues with some projectors which used to work before, see:
https://bugzilla.redhat.com/show_bug.cgi?id=1236337
The user reports that going from 4.0.5 to 4.0.3 fixes this, and 4.0.5 is the release where the revert landed. I've inspected the EDID of the projector and drm_detect_monitor_audio() should return false for it.
Adding radeon.audio=0 to the kernel cmdline fixes the pink line.
Regards,
Hans