Unsolved User Registration and Login (SSO by default)
Prioritizing SSO seems to make a lot of sense. Simplifies and speeds up authentication and encourages user registration by replacing typing in email/password with simple click/tap and accept.
It would be nice to have a switch to reverse Email/SSO priority and a link to reveal (unhide) email registration. There is a solution pointed out by @PitaJ but using CSS will not allow auto-translation and may be uncomfortable for some.