Google requires completing authentication in Safari for my Google Mail

I contacted Apple Support about this. Apple Support acknowledged that this is a software defect that their engineering team is working to fix. Unfortunately, Apple Support refused to provide a way to track when the issue is resolved.

This appears to be related to the recently released Safari update (v13)... it was working fine for me on 10.14.6 until I applied the Safari update.

Got this today as well, after updating to 10.14.6. I have both personal as well as business related emails via Google, and none of them work. Same with iCal. Going to Safari, literally, does nothing. Tried also via all Google accounts, passwords, settings -nothing.

Tried:

1. removed keychain history - didn't help (won't let reenter passwords on Mail, won't enable, won't take online)
2. going to google account security and turning on less secure apps - didn't help (was recommended at google forum)
3. removing/re-adding the account to Mail - didn't help (won't let adding google-related account back; also not via "other")
4. disconnecting iCloud account and re-connecting - didn't help

All calendars of course off, as well. Using emails via browser at the moment and downloaded Outlook (a pain!).

HELP, Apple? This seems to be reoccuring issue for updates since 10.14.4 as forums show. Running on early-2015 Pro.

Found any solution for it?;)

Roger. Fingers crossed. Meanwhile, gonna try to survive on Outlook. ****.