Nvidia has some official "G-Sync compatible" listing.
Though suspect they're not entirely honest and expect some monetary transaction from monitor maker to get into that listing.
(wouldn't wonder dirty tricks in drivers)
Anyway there are lists in web about how compatibility with various monitors.
And newer monitors tend to work better.
No surprise that some half assed just barely functional FreeSync monitor wouldn't work without issues with Nvidia card.
It can be enabled manually in drivers for any monitor claiming FreeSync:
https://www.techspot.com/article/1779-freesync-and-nvidia-geforce/
Also Nvidia doesn't support FreeSync over HDMI.
