As others are saying, OSMC might work. Most difficult part is making it so that the TV turns on when you turn on the computer since ARC isn't a thing for most computers.
I ended up giving up on OSMC and bought an Apple TV since nothing else got the "wife approval" factor. It's better than Google getting my data, has a Plex client, and let's me stream my Steam library.
Sure, you can use a VPN if you want to spin up the instance and connect to it without having a domain. You can always open the instance of Nextcloud to the internet later, when you buy a domain.
Get a cheap .XYZ domain if you just want to experiment with spinning up a reverse proxy.
I don't know what your - and your kid's - situation is, but I worry pushing Linux onto someone would be counterproductive to getting them to like it.
I only use it because I genuinely like and appreciate it. I'd probably start by getting him interested in it. If he likes it enough then he'll try and learn more by himself.
I recently got an LLM running locally on an AMD GPU. This was only possible on Linux. Depending on your son, something like that could be a cool way to get him interested.
Not yet, although not for lack of curiosity. I was busy at the time and then forgot about this.
Although, in case you're curious, tomato cake is a thing I've made and it's definitely different. I didn't like it at first but I also ended up eating the whole thing over a couple days.
As others are saying, OSMC might work. Most difficult part is making it so that the TV turns on when you turn on the computer since ARC isn't a thing for most computers.
I ended up giving up on OSMC and bought an Apple TV since nothing else got the "wife approval" factor. It's better than Google getting my data, has a Plex client, and let's me stream my Steam library.