I ran Konstakang LineageOS on a RPi4 a few years ago, but the hardware decoding didn’t work well. It might work better now. I will probably use Bigscreen once it’s available in an immutable or LTS distro, but for now, I’m using Pegasus frontend on a Linux mini PC. It’s clunky, but kind of gets the job done. Jellyfin desktop and VacuumTube work ok, but I mainly use it for games anyway. I really want Linux HTPCs to be worthy of a daily driver, and Bigscreen is the best hope as you said.