Just buy a tv that has the features which within your budget. Don’t connect it to the internet if you don’t need that. Get an Apple TV or other desired streaming stick if you do but some or most will some form of ads or tacking.
You could look at setting up pihole or adguard home server to help minimise internet based ads & tracking but it may not stop all.

Sounds like you’re just starting out. If you’re not yet familiar with Linux there’s a lot guides out there to set this up & it won’t take take long. It’s when things go wrong it can be frustrating as it possible there won’t be a guide for your specific issue & it can be time consuming to figure it out.

You could start just using windows if that pc came with it. It’ll enable you fast track the fun of building & populating the media server.

Over time you’ll discover the limitations of windows, start researching the alternatives & have plenty of time to pick something else while enjoying what you’ve already setup.

The thing is, many people will show some interest in this but ultimately don’t want to do it themselves. It does require varying amounts of time to learn & most importantly to fix it. Many people are time poor or would use their spare time on other stuff.
You should ask whether they’re genuinely interested in setting this up & if so what the concerns are.