LNER have already been telling people that they have to mask up on stations, which as far as I am concerned is total bs. They've restricted replies to the tweet though.
The new regs have arrived. Hurrah :-/
https://www.legislation.gov.uk/uksi/2021/1340/pdfs/uksi_20211340_en.pdf
As far as I can see, basically exactly the same as before, definitions, exemptions, fines, etc. So no, no legal requirement on stations as far as I can see.
They've folded in the signage requirements into this one too, which used to be in a mostly unrelated regulation. As far as I have ever read that one, it means that signs have to point out the existence of excuses and exemptions, and it is an offense if they don't.
They do expire (for now) on December 20th, so they will have to either explicitly remove or extend them in 3 weeks time. Which is something I suppose.