Seems a strange story. EU residents living in the UK were offered the EU settlement scheme which allows EU residents to live here after 30 June 2021. Free to apply and millions of EU residents have done it. Would have thought there would have been a reciprocal agreement for uk residents living in the UK.
The EU Settlement Scheme for EU citizens and their families to remain in the UK after it leaves the EU ('Brexit'): who's eligible, how to apply, how much it costs.
www.gov.uk
Residence rights for UK nationals and their family members in the EU and EU citizens wishing to live in the UK since Brexit, exceptions under the withdrawal agreement, and information on applying for an electronic travel authorisation (ETA).
europa.eu
Says here all they had to do was apply for a biometric card. So very strange