Hi there
It’s difficult to tell if a non mask wearing person is just being ignorant, Or has a genuine hidden disability. Why not wear a “hidden disability lanyard”, all supermarkets supply them at the customer services desk. They’re recognised in the UK shops, banks, high street, airports and supermarkets. They’re bright green with big yellow sunflowers. It worked for us for mum when we took her out pre-covid, as she would get lost in the supermarket, or shout at people randomly and make nasty comments. It would maybe save a few arguments in the shops?