I used to use RiMusic, would stop working for me as well.

OpenTune has been working for me for a very long time without issues.

Yeah. I agree that social media isn’t good for kids (or anyone). But this implementation isn’t well done. :/

The kids probably like a huge variety of newer music you wouldn’t get on disc but mentioning just in case. I noticed Kmart is selling discmans and little cd players fairly cheap. You have the benefit of knowing what they’re listening to.

A better option is iTunes and a secondhand Shuffle.

Just remembered there’s stuff like Grayjay or Revanced?

I can’t tell you much as I haven’t used them myself but apparently Grayjay can play a bunch of videos from different sources. However there are mixed reviews and it’s android only. The ability to allow age restricted videos seems to be broken though so maybe that’s a plus 😂

There’s also some non-app based measures to manage YouTube without an account https://www.clrn.org/how-to-put-parental-controls-on-youtube-without-an-account/