Thanks!
I'm already using Jellyfin, and it's the Jellyfin Media Player app that is playing the file.
I'm using pipewire to handle a surround sound setup, since I don't have a separate receiver, and just got a TV supporting HDR.
I'd use the Apple TV... But that doesn't handle the sound without a passthrough receiver. ๐
Ah well, I was hoping to avoid having to buy a receiver, but maybe that's just what I need to do..
And the HDMI outputs too!
I use a combined audio sink.
Oh, and there might be a way to get Dolby Vision data out to a monitor, as per this:
https://www.reddit.com/r/linux_gaming/comments/1d6zvb9/how_come_hdr_and_even_dolby_vision_work_in/