I have my company G suite, and the new version of Hangouts is called 'Chat'. Where Hangouts would auto rotate for easier typing, this app will not. Not a showstopper, but seems to me it should be able to. I've check the settings, and it just won't.
Ah, I see. Sorry, I had the full name "Hangouts Chat" stuck in my head, so "Google Chat" didn't quite register.
Unfortunately, I don't use G Suite, so I can't test that out. I assume everything else auto-rotates correctly? Have you tried clearing the cache/data from the app?