At first it was annoying because we lost focus and then we decided it was better and ended up being good discussions in two groups as long as we compared notes after between the groups.

Helsinki meetups have had a habit of explicitly breaking people into small groups (of about three people), letting them discuss the current topic for a while, and then breaking up and re-forming new groups so that everyone ends up talking to people they didn't talk with in the previous round. Repeat this until out of time.

Seems to work okay and is also useful in making sure that the quieter/less assertive people also have a chance to speak. I like to imagine it also helps reduce groupthink, if we ever were in a situation where that was relevant, because a person who proposes an idea in one group won't get to spread their idea to other groups until before the people in the other groups have already considered different ideas.