When my mom got to the point where she had trouble identifying what was going on TV, even relatively innocuous things became problematic. She somehow got hooked on the History Channel and then I started getting weird requests from her based on what she'd seen on Ancient Aliens 🤦‍♂️

I don't know what the True Neutral of television is, but some potentially safe random things that come to mind: Bob Ross, concerts (symphonic maybe? Could take some ideas from the guests on the Muppets)... you could load up on ambient sights/sounds like https://www.amazon.com/Soothing-Stream-Ambient-Nature-Video/dp/B01MTZ3YPQ which are common in hospitals.

I wish I had some better ideas because I could use them myself, although my mom hardly pays attention to the TV anymore.