There are many British in Portugal who don’t have Portuguese residency, so for whom the Schengen rules now apply, since Brexit. We asked the British Embassy what action they need to take and their reply is below.
"Although we understand the difficulties in travelling at the moment, Covid travel restrictions have been in place for some time, and the more recent flight ban between Portugal and the UK as well as the introduction of hotel quarantine, do not prevent UK nationals residents in the UK from returning home, though they have to use a non-direct route. UK nationals are still allowed to enter the UK.
Furthermore, even though the hotel quarantine may have created a new layer of difficulty, advanced notice was given on this measure so travellers could prepare for this situation.
If a UK national who is normally resident in the UK is still in Portugal and has questions about staying longer than the 90 in 180 day visa-free stay, they should contact the Portuguese Border and Immigration Service (SEF). The Portuguese authorities are responsible for the implementation of the Schengen Borders Code rules in Portugal.
I hope this helps better explain the situation. As you’ll understand, we are unable to comment on the enforcement or penalty policies of Portugal or in the wider Schengen Area."
British Embassy, Lisbon