In the meantime I think as a workaround I think you could use
something like video=HDMI-A-1:e on the kernel command line (not sure
I got the connector name right for your system). I think that should
result in the live status check to be skipped, at least when
populating the mode list.
Might be a good idea to collect all the information here and put in a
bug report (https://bugs.freedesktop.org/ -> DRI -> DRM/Intel) so that
all the logs and such would be in one place.