Been checking How Brexit might affect (and new requirements) me as Brit living and working in Germany. Up till now GB Passport Holders would have been working living with the Authorisation under the EU rule “Bescheinigung gemäß § 5 FreizügG/EU” basically the recognition of your EU status.
on Gov.UK i found this:-
Your rights under the Withdrawal Agreement will not be affected if you do not meet the deadline. However, we recommend that you obtain your new card as soon as possible.
You will need a valid UK passport in order to obtain your residence document. Find out how to renew your UK passport from Germany.
There are over 600 Foreigners Authorities issuing residence documents throughout Germany, so processes may differ from town to town. Some Foreigners Authorities have already set up a reporting process for UK nationals, whilst others are not taking any action yet. In some areas, Foreigners Authorities have written to UK nationals. If you have received a letter, you should follow its instructions.
You should contact your local Foreigners Authority to find out how to obtain your residence document. You can also check links listed on this page to see if your Foreigners Authority has published guidance for UK nationals.
If you have contacted your local Foreigners Authority but have not yet received a response, it is likely that you will get one in the next few months.]
I will contact my local “AusländerBehörde” for confirmation when they are available.
on Gov.UK i found this:-
[Get a residence document
If you are legally resident in Germany by 31 December 2020, you should obtain a new residence document (Aufenthaltsdokument-GB). To get this document you must report your residence to your local Foreigners Authority (usually called Ausländerbehörde) by 30 June 2021.Your rights under the Withdrawal Agreement will not be affected if you do not meet the deadline. However, we recommend that you obtain your new card as soon as possible.
You will need a valid UK passport in order to obtain your residence document. Find out how to renew your UK passport from Germany.
There are over 600 Foreigners Authorities issuing residence documents throughout Germany, so processes may differ from town to town. Some Foreigners Authorities have already set up a reporting process for UK nationals, whilst others are not taking any action yet. In some areas, Foreigners Authorities have written to UK nationals. If you have received a letter, you should follow its instructions.
You should contact your local Foreigners Authority to find out how to obtain your residence document. You can also check links listed on this page to see if your Foreigners Authority has published guidance for UK nationals.
If you have contacted your local Foreigners Authority but have not yet received a response, it is likely that you will get one in the next few months.]
I will contact my local “AusländerBehörde” for confirmation when they are available.