A few years ago, before Google introduced YouTube music, they had the Google Play Music app that let you listen to their entire catalog, download/cache the songs beforehand, listen to your own audio files on local storage (including .flac files), and subscribe and listen to Podcasts.
Literally was one of my most used apps until YouTube Music happened and they had less features for double the price.
You can permanently activate it with the scripts from massgravel: https://github.com/massgravel/Microsoft-Activation-Scripts