Despite the promises that the UK was going to leave today, 31st October 2019 "do or die", it.... hasn't.
The Brexit saga continues.
The UK has yet again extended EU membership, this time until 31st Jan 2020. Meanwhile, the UK parliament has agreed to hold a general election on 12th December 2019. It hopes to break the deadlock and achieve a majority for something - either passing the new deal Boris Johnson agreed with the EU, or some kind of renegotiation and a second referendum.
Either way, it looks likely that freedom of movement would continue at the very least until the end of the transition period (December 2020), which gives those UK citizens who wish to move to Portugal a bit more time to do so under EU terms.
If you would like help with getting a NIF, setting up a bank account, registering your residency and obtaining healthcare in Portugal, please contact me.