Just tried it - it works on my Samsung C34F791, which is Freesync compatible, and RTX 2070.
I had to switch G-Sync on in nvdia settings and pick full screen and windowed mode (full screen option did not work in full screen DCS).
I also had to pick FreeSync Standard Engine in monitor settings, Ultimate one gave me flickering.
Would be good for others to confirm if their FreeSync monitors work even if they are not nvidia approved!