In reply to Mr. Lee:
Unfortunately this time they specifically address the uk in their FAQ on the immigration/travel website so its not an oversight (as below). Yes they are still applying a quarantine to most of Europe but since I can work from a laptop or travel from Denmark it was still going to be a possibility.
Brexit: I am a British citizen or a citizen of another country and a resident of the United Kingdom. Can I still travel to Norway after 1 January 2021 if the corona restrictions still apply?
No, you can not, unless you belong to one of the exceptions who can enter or are a British citizen residing in Norway and have legal residence before 31 December 2020.
The United Kingdom left the EU on 31 January 2020. According to the immigration regulations, when the transition period expires on 31 December 2020, British citizens will no longer be considered EU/EEA citizens. This means that British citizens and other citizens residing in the United Kingdom cannot enter Norway after 1 January 2021 unless you belong to one of the exceptions for citizens living outside the EU/EEA to which we have linked to above.
Post edited at 07:26