Comment 3 for bug 1957944

At the moment it's "Yaru-dark / Yaru" and the issue remains.

I was using a third party theme when I first encountered this. I switched back to Yaru before filing this bug, but about:support was still showing the third party theme. After resetting the theme it's showing "Yaru-dark / Yaru".

I did some more testing with a separate login I use for steam and a new FF profile. It seems to only happen when a a FF colorways theme is used. If the default theme is used I am able to see a difference in the titlebar shade (it's too subtle IMO, but I can see it).