Most solutions require either the consent of the talker or that they not be present. For example, one solution is that the group splits into multiple subgroups, so that multiple people can talk at once- but there are ways for the talker to counter that, like abandoning their subgroup to join another subgroup (effectively merging the two) or asking people to keep to one conversational thread.

There's a broad blunt-subtle continuum of ways to communicate to someone that's they're dominating the conversation, and it generally seems best to use the most subtle option that they'll actually notice, but again, communicating to someone that they're dominating the conversation doesn't mean they'll stop dominating it.