I gave my kid a second-hand https://www.ocarinaplayer.com/en/ (just discovered they went recently bankrupt) and we all love it. It's quite simple to use, basically just an old-school MP3 player with a USB port. Physical buttons, quite simple interface. Works.
I just don't really like how they treat the jack port: you have to tell if you're using it for mic or for headphones each time you plus something in.