What is the social dance form that needs no partner, is "for as many as will", and can maintain 2 metre separation?
Apart from the separation issue ceildh seems to be going that way. As a Knees Up regular I have noticed an increasing reluctance to ask strangers to dance. Instead people often just walk into a set and stick their hands up.

I think it may partly be down to so called gender free calling which presents folk dance as junior school music and movement rather than as a social event.