You are still likely going to want some sort of streaming device though. I have an old computer of mine running unraid with Plex in a docker container and still use a chromecast in apps only mode to stream to my TV.
Oh yeah, I already have a Chromecast. I know this is a post about Roku specifically, but it was just another example of enshittification getting me to finally set up my own system. It was honestly the HBO Max disaster that got me started.
Good to know about App Only Mode, though! So far the Chromecast interface doesn't bother me, but it's good to know there's a ripcord I can pull if it gets worse (unless they take that away).