There are other ways to do it, too. I use a command called __GL_SHOW_GRAPHICS_OSD=1. That way, you can use it in only the stuff you want, like games, not Firefox. Also, from my understanding,
it only works in OpenGL. I can be wrong about that, and my understanding is
the Game OpenGL versions have to support it before working. I have to look into it more, but this is my understanding of it from the little I know. Also, you can turn on VBLANK with __GL_SYNC_TO_VBLANK=1
Edit:
I fell over this post. I don't know if that is going to help any.
https://www.reddit.com/r/linux_gaming/comments/hb8w7n
I have done some testing in Steam Flatpak. Halo Infinite with VK3D3 has Flipping, Half-Life 2 (native) also has Flipping, and Metro 2033 and Metro 2033 redux have Flipping. And Euro Truck Simulator 2 has Flipping. I'm on Garuda with the 2070S and Driver version 515.65.01.