> from a dedicated unprivileged user, so it can't do any harm beyond recording my conversations

Unless I'm misunderstanding what you mean by that, I don't really see the point in it, TBH.

Have there been cases of Zoom infecting machines with malware or transmitting viruses? The whole concern, as far as I know, is terrible security on their end, allowing people into calls without permission, not having E2E encryption, etc, and running as an unprivileged user won't help with that at all.