This could just be an issue with my corporate account, however just after Beta 2 upgrade yesterday all three of my iOS devices prompted me to re-authenticate to Microsoft 365. The authentication (2FA using Microsoft Authenticator app) worked ok, however I'm then prompted with the "Need admin approval" screen for "Apple Internet Accounts", then prompted to provide an admin account to authorise it (I'm not an admin).
I'm using native mail/calendar/contacts with M365, and this was all working just fine with iOS13 and then iOS 14 Beta 1.
Anyone seeing a similar issue or have ideas on what to fix.