Correct, only EU citizens and permanent residents in Germany were allowed to enter the vcountry during the COVID lockdown periods. My guess is that the OP never applied for German permanent residence before the 1 Jan 2021 deadline, when freedom of movement across the EU ended for UK citizens. For one thing, there's a reason why we have national ID cards in the EU/EEA, and needless to say, a rental agreement doesn't prove squat, just ask the British-South-African couple living outside Lisbon who were detained in Frankfurt airport the other day.
https://www.theguardian.com/politics...rexit-id-cards