How can British citizens prove they're resident in Sweden post-Brexit?

The UK has left the European Union but most changes don't come into effect until December 31st this year. The Local has looked into where British citizens will stand after that date, the documents you'll need, and what we still don't know. https://www.thelocal.se/20200831/how-can-british-citizens-prove-theyre-resident-in-sweden-post-brexit