After intensive negotiations, the European Commission has reached on 24 December an agreement with the United Kingdom on the terms of its future cooperation with the European Union.
Even with the new EU-UK Trade and Cooperation Agreement in place, there will be big changes on 1 January 2021. The Government of Flanders is doing everything in its power to prepare companies and citizens for the end of the transition period. On https://www.vlaanderen.be/brexit (in Dutch only) you can find a useful overview of the upcoming changes. This page is being updated regularly.
For information on the rights of EU citizens in the UK, you can either go to the website of the Embassy of Belgium and the Delegation of the European Union to the United Kingdom.