You can force it to do that if you really want to, but by default it will speed it up to 24.00fps and play it alternating between 2 and 3 screen refreshes for each frame (i.e. 3:2 pulldown without the interlacing).

Is there any way to make it work with adaptive refresh to play the video at exactly its native speed and adjust the display refresh rate instead? Or should that just work automatically?

VRR support for MPV is disabled by default in /usr/share/drirc.d/00-mesa-defaults.conf. I am not sure why, because it works for me if enabled. Just fullscreen MPV and it will change the display refresh rate. This requires VRR enabled in both Xorg and your monitor's settings. I have not tried this with Wayland.

I have no idea why I wrote 30, when I was thinking 24.

Thank you for the answering the question I didn’t manage to pose!

No, I forget what the exact limit is, but it does change the speed more than ~0.5%. So going from 59.97 to 60 or vice versa, but not 24 to 30 or 50 to 60.

But Yeah, I am in LOVE with this feature, even for 30fps footage on a 60fps screen. The more stable frame times make a huge difference.

No.