I spent a lot of time trying different distros, and all sorts of different things. H.264 was no problem, that definitely handles them properly. But with H.265. I've got to the point where the modules that seem to contain the H.265 support load, but throw experimental warnings all over. But they still usually either: don't work at all, or make the OS blow up.
I just gave up after hundreds of hours, since my decade old RPi 3 seems to do the equivalent with a lot more stability.
I'm just checking back every 6 months or so. Since I'm fairly sure this processor is capable of it. (But so far, that OPi4 LTS purchase was a complete waste for my purposes.)