Because I'm reckless like that, after I got the GA version mismatch error, I just went ahead and installed the latest versions of all of the pods. Don't get mad.
It all seems to work fine, except sometimes the password textfield will turn square and a pale yellow and have the text "strong password" (I think. I should have written it down). I've tried replicating it a few different ways (poor password, malformed email, etc.) but can't seem to figure out why it happens.
The user registration works fine, showing up in the Firebase console.