Usually, there are two screens for a Microsoft signin. I think we may be able to reduce it to one screen (I need to talk with @Harry about this).
In your case, I believe your have configured your O365 service to use Okta as the single signon. So there is now one more indirection to Okta (which produces your third screen).
The only good news in this is that once the user is signed in, they don’t have to do it every time the app is used.
Another possibility is that you could set up the app to use Okta signin directly (AppSheet supports that), and perhaps that would be better than using O365 for signin. The app can still work against data in O365, but the sign in could be via Okta.