Lorna - yes, you're right of course, these things are probably different for men - however there are going to be similar issues.
If I went to something like that and got chatting to a woman for a while, then I would be concerned that her OH was jealous. But I wouldn't make a move, I wouldn't invite them out for a drink later, and a while after noticing him being jealous over in the corner I'd move on and talk to someone else.
But I wouldn't feel bad for having a conversation with someone interested in me. The guy would obviously be an insecure dick who shouldn't be going to a MeetUp thing if he didn't want he or his wife to MeetUp with new people.
I'm not responsible for other people's issues, I'll talk to people who are interesting, and who find me interesting. I'd politely talk to the schlumps but decide who I wanted to talk to, not be 'pushed' by anyone. And if people choose to judge me for being overly flirty, when I'm just chatting to people, they can get bent.
Different meetup groups will have their own dynamics of course, and I understand it's different for women, but I'd still say to just ignore people who are pushing you towards schlumps, decide who you want to talk to, and talk to them. You're a strong independent woman and can talk to whoever the hell you like.
If people have a problem with that, they don't have to talk to you. Maybe they should leave their husbands at home if they can't trust them.