If you are interested in standalone digital audio players (DAPs), I just recently bought this:

https://www.fiio.com/echomini

For ~$60 you get a device that can play every type of audio file and has better sound quality than your cellphone + streamer combo.

I've been reading more about Chinese hardware and if you've been sleeping on it there are a lot of great Chinese consumer products that are both extremely high quality + very cheap.

Turns out when you have tens of millions of engineers they pump out banger after banger. Also always hilarious, in an enduring way, finding the factory engineers engaging with consumers on random forums that take their feedback seriously.

If they're allowed and help where phones wouldn't or don't there are still lots of options for stand alone MP3 players with minimal or no connectivity. They still exist as a market because they're dirt cheap to make.