https://bugzilla.kernel.org/show_bug.cgi?id=207901
--- Comment #25 from Lyude Paul (lyude@redhat.com) --- Hi! could you please retry this with a kernel from drm-tip? I don't see any DisplayPort/DP MST debugging output there, so I'm guessing you either forgot to add drm.debug=0x116 or your kernel (which appears to be based off the ubuntu kernel) is too old to support that. As well, I can see a couple of other bugs from nouveau in that log which have already been fixed in more recent kernels.