Chat in breakout rooms not available with the old version (Teams classic)

Hello,

We are mostly using the new Teams version, ie Teams (work or school), within my company. When we create breakout rooms, our internal users have access to the chat within those rooms, even if they use the new Teams app, the old Teams app or the web version.

But external users (outside our company) must use the new Teams app or the web version. If they use the legacy app (classic), they don't have access to the chat.