Truly uncanny!

Only the British audio works for me, though - if I try American or International, the relevant meetings are silent with a "Join Audio" button which doesn't appear to do anything. (Firefox on MacOS, if that's useful)

Yeah we need a dial to mix accents and dialects, and level of English fluency. I could want 50% English, maybe some Northern English, Welsh or Scottish, and mix in Indian accents, various American, Spanish, Portuguese, Polish, Scandinavian, the odd token Aussie. Etc.

That I could enable more South African, or Middle East accents in some meetings would be true to real life as well.

Not Finnish. The silence would not work :)

Same, console says something about missing or "unsuitable" audio resources.

Sad, I wanted the international broken Zoom call

Same here - Brave browser. Only British works