How does it work in practice, though? Would German immigration officers ask for evidence of where in the US the traveler is living (e.g., drivers license) and instruct those from US states on the risky countries/states list to follow the quarantine rules of their destination state?

Seems to me if you are quarantined in a hotel in Hessen, you won’t be able to visit family in Bavaria.

A possible solution would seem to be to get a covid test done right before departure and then stay in Bavaria. The test would seem to be advisable anyway.

Whatever happened to Lufthansa’s announcement of offering tests in FRA and MUC for arriving passengers?