Take this with a huge grain of salt, but I remember hearing once that the eyes are kind of an external piece of the brain.
ProperlyProperTea
I have an RX6800XT and I use KoboldCPP to run models I download off of Huggingface.
I'm not sure how many tokens per second it generates, probably about 10?
If you want to try it yourself here's a link to the Github page: https://github.com/LostRuins/koboldcpp
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.
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.