As far as I understand it, post-Brexit EU residency granted to a UK citizen allows them permanent residence and right to work in their chosen country.
They don't have the right of freedom of movement and cannot simply go and work in another country as they could before Brexit.
However, can they work remotely (ie. remain resident in their original chosen country) for a company based in a different EU country?
I can't see why this would be a problem (income tax would be paid in the country of residence as usual) but neither can I find any information which definitively states one way or the other.