Any Linux distro with Plasma Bigscreen. My TV box is an old laptop I got for free from work running Cachy OS. I have a remote-sized keyboard/trackpad that I use to control it. I mostly just need the arrows, but the whole keyboard is there if I need to go in to the desktop OS.

I could use a recommendation for a big-screen ad-blocking YouTube app though.

Any post-2015 laptop would work. Look around in your local recycling bins :D