One possible solution is to use any old phone to run Plexamp app. Used to require paying for Plex Pass, but it is now free. Check it at www.plex.tv/plexamp/
How it works: You would need to run a Plex server on your machine. Plex allows you to also get missing metadata and cover art, some of it automatically, and to have the Plexamp app to pull all the music you want from your machine and can fit in that phone.
Then turn off WiFi and all music will be on that device with cover art and metadata. I think, not sure, the only thing that it may not have while off of the internet is lyrics, but I might be wrong.
Leave Bluetooth on and you have the device with all your requirements: music with art cover on intuitive interface, off the internet and Bluetooth capability.
Others reading this can vouch for or make additional suggestions.