Hi,
I've an R9 r390 graphics card , an Epson EH-TW7000 Projector and driver version 20.11.2. Unfortunately, I have black bars at the edge of the projected screen (underscan). I already found this article: https://www.amd.com/en/support/kb/faq/dh2-022 . But I cannot find the setting for adjusting HDMI scaling, it seems to have disappeared. Furthermore, the proper native resolution (3840x2160) is not detected: My windows display options does displays 4096x2160 as the recommend resolution.
I connected the projector to my notebook with the same HDMI cable, and the problem does not occur. Neither on Windows 10 nor Ubuntu - There are no scaling issues and the native resolution is also detected properly.