I bought an ASUS PG259QN which is a hardware gsync monitor, and it also supports freesync over displayport.
Edit: Looking into it Nvidia apparently opened support for freesync on gsync monitors at some point after November 2019:
Share this contentIn the last year we’ve seen a distinct change to NVIDIA’s approach to variable refresh rates (VRR) and their ‘G-sync’ technology. Historically there was a clear demarcation between....[click link for more]
www.tftcentral.co.uk
So it's worth checking if your monitor was released sometime after that.