That happened to my sister unfortunately. She tried to transition her account and kept getting strange errors and minecraft support was very unhelpful. I ended up buying her a new account for her birthday, which I’m glad we can play together again, but it sucks that some strange bug took her account in the first place.
I forget what it’s called, but there is a 3rd party application that allows you to play the mobile version on Linux. I only use it to play with my cousin since she can only play on Xbox, and it works pretty well.