As a variation on the explicit "I'm ending my talking turn", maybe use Aesop-style summaries as the marker, using some kind of agreed-upon lead-in, like "and that's why..." That could be useful for a number of reasons:

~It would definitively mark that the speaker was done talking

~It would encourage one's thinking to be more focused. If you can't briefly sum up what you've been saying, then maybe you've been trying to say too much at a time. This isn't always a problem, but it could lead to your conversation partner missing something.

~It serves to signal what the speaker themself thinks is important or more tangential, which may differ from the ranking the listener inferred. This could become a talking point in itself, either for clarification or for a more meta analysis.

Thoughts?