@KinkyKobolds That's interesting! I should have mentioned that the option is there for me in the KDE Display panel, it just doesn't do anything. I tested it with my monitor's built-in FPS counter: With only one monitor and VRR on the framerate varies as expected, but with multiple monitors it stays stuck at its maximum refresh rate and things feel "choppy".
People in this thread are reporting the same issues, so it seems I'm not alone at least, hah:
https://forums.developer.nvidia.com/t/feature-g-sync-freesync-under-wayland-session/220822/5
Glad to hear that it's working for you though! I wonder if it's something to do with how laptop graphics are set up - I know that they often have their internal display hooked up to the integrated graphics. If the Nvidia card has to go through the iGPU, maybe that results in it only seeing a single "direct" display (the external monitor)? Just a guess hah, sorry for the long response