about a month ago I had the same problem with AOC monitor which I ended up replacing with this one.
I connected the new Samsung monitor with HDMI which came with it (as it says I should in their manual), I downloaded the drivers so it doesn't show as Generic PnP, I turned it on in the OSD (both standard and ultimate freesync option), I clean installed the AMD drivers again but nothing seems to work, it still says "freesync not supported" in the settings.
Only issue that I can think of that might be causing it could be that when I updated my AMD drivers it said it had been partially installed, error 1603. I troubleshooted all points from here but couldn't get it to "fully" install (although everything else seems to be working just fine even with "partially" installed drivers.
Any help is appreciated!
My system info:
Did you try using a display port connection instead of HDMI?
Monitor has HDMI and VGA outputs only.