I’ve never seen it work except in first party apps. YouTube, plex don’t support it, maybe Jellyfin does but I don’t remember. I’m betting it comes down to whether you use the built-in frameworks for video playback or bring your own.

Yeah I'm aware it's hit-or-miss. But I use it in Infuse, which is a third-party app that supports it, even with its own framework.

And now that Plex laid off the entire player dev team, I guess we'll never get that feature :(