Apple Music in europe
Do you need internet for it to work or will ATT cellular allow it to work
also safe to Bluetooth music on airliners?
Check with your cellular provider as to what agreement they will have with the European service provider.
The other question is, will it work at all?
Legal - Apple Media Services - Apple - September 12, 2022 "Our Services are available for your use in your country or territory of residence (“Home Country.”)"
and,
"Certain Services and Content available to you in your Home Country may not be available to you when traveling outside of your Home Country."