IMPORTANT (1st July 2020)
The Luxembourg government has now released information concerning the procedure for the application for the new residency document (card) for UK citizens covered by the WA.
Please refer to Guichet.lu :(https://guichet.public.lu/en/citoyens/immigration/plus-3-mois/ressortissant-britannique/document-sejour-ressortissant-britannique-membre-famille.html) for more information.
All foreigners arriving in Luxembourg have to register with their local commune. The procedure is straight forward and welcoming.
You must do this before applying for the new residency document (card).
Newly arrived? Find out more here (in English):