Do they? To my knowledge London Amateur Brewers has never charged any kind of fee and I’ve not heard of others doing so.Well most clubs charge a subs/dues so that's one way to keep spammers out.
I wouldn’t worry too much about spammers - in the three years we’ve been running zoom meetings we’ve had one invader and that’s despite keeping the meeting ID and passcode the same. They were swiftly booted out and we turned the waiting room feature on. We still haven’t changed the password and they’ve not come back again.
The only thing we do is ask people to email or message us to get the passcode.