Hi,
A bit different my scenario.
I'm British and have lived in Greece since March 2002. Have had residents permit since then. Decided in summer 2020 with my partner of 31 years that we would like to move to Spain.
Started the process of selling our house in August 2020. Partner moved to Spain in September 2020 and started residency. I was due to follow in October after house sale. October, Greece introduced COVID restrictions and the government buildings were closed to the public and went appointment only. This delayed the buyer paying the tax on property until late December 2020. Sale can't be completed without tax payment.
Anyway, I'm now only able to travel to Spain and join my partner. I thought everything would be OK as I had read a document online from the Spanish Embassy Here that stated in the "Brexit Update" paragraph, and I quote "However, UK nationals and their family members who established the residence in other EU Member State before the end of the transition period in accordance with EU free movement law, will maintain their free movements rights after 31st December 2020"
I contacted the Spanish Embassy in London and made them aware of my situation and asked for travel advice, but, they say as a British Citizen I can only enter Spain for a period of 90 days. If I wish to stay longer or reside there I will have to apply for a visa.
So, it appears they are not honouring the fact I have been resident in an EU country for almost 19 years prior to the Brexit transition period.
I would take any of these "Official" documents with a pinch of salt at the moment as no one seems to know what they are doing.