Oggyo You seem to have exactly the same story as me, so this is very interesting!
You are saying I may have jumped to conclusions about MS Authenticator requiring Play Services?
( Installing them though Aurora, and transferring the license was painless IIRC. )
I seem to recall that Authenticatior without GPS did not work for the enforced second factor for logging into O365 / Azure, and that I had to install it in my GPS profile to make it work for that. I guess I will have to try again now!
(TOTP with Bitwarden was impossible to get working)
Although I have to say that Authenticator working as a "local broker" creeps me out a little. I thought I knew a bit about how Oauth2 works, having implemented several "flows" in a web context, and I don't recall anything about apps talking locally among themselves! I also notice that Authenticatior has registered my work account on the Android level as a "work account", and I hope that does not come with any form of device admin privileges! I may need to read up a bit more on how all this works!