> Clubhouse is one of the very few online places I've seen people willing to speak frankly on sensitive political issues in Chinese, perhaps because Clubhouse rooms are (at least nominally) ephemeral, leaving no record.

I don't think that's a reasonable assumption since the invention of screen recorders, especially combined with Clubhouse's "real name" and a "real face" policy (I'm not sure if the latter is official policy or just a community convention, I'd be more worried about the former)