Yea there's very little public information on hacking anything other than android boxes and most of the more extreme stuff will break apps like Netflix or Disney+ so the best thing to do it leave it effectively stock, load on a hacked youtube client, with a dummy google account if you really want it private and your personal streaming client of choice (Plex, Jellyfin, Kodi etc) and then do some filtering/ad blocking in your network to lock it down.

The only caveat with an SBC is codec support varies greatly between distros you use on them, and you have to work out your own control/remote situation. I moved away from them for media a few years ago because I was sick of having to tinker and reinstall things because some codec was broken or the screen was tearing, or an update broke something requiring terminal access to fix. If you want a proper home theatre setup with full HDR and lossless surround support it's not worth the trouble.