Apparently so it does, and it says “HDMI Freesync” rather than “HDMI [2.1] VRR”. FreeSync HDMI is a completely different protocol and is supposed to work under Linux. Found a thread here, can you try cat /sys/kernel/debug/dri/0/HDMI-A-1/vrr_range
and edid-decode < /sys/class/drm/card0-HDMI-A-1/edid
? Though there is no solution there.
It’s 401 unauthorized or 403 forbidden, not 403 unauthorized