4 monitors on an M1 Mac HD 1080p

I'm running 4 monitors at once on an M1 Apple Silicon Mini, with 16 gigs ram, a $15 used Gen3 AppleTV, and a $100 Startech usb to dual DP converter. A mix of 4k and 1080 monitors, and everything is working except Final Cut.
But I can get FCPX to work with 3 monitors just fine, and even use Sidecar as a 4th monitor with Final Cut. So don't believe that info that the M1 only works with 2 monitors.