Perfect question as I just upgraded.
I wanted an actual high quality monitor so I got the LG 34GK9501F only to realise after installing that my GTX 980 TI Golden Edition didn't support Freesync over G-Sync DP. So I was like, shit I got this magnificient monitor I got specificatlly for G-Sync so I just received today my new RX 5700 XT GPU, just a bit better than my old but I can finally use Freesync.
TL:DR I had to Upgrade from 980 TI to RX 5700 XT for a compatibility technicality.