I've noticed this morning that all my Gmail accounts in Mail are failing authentication again. This last happened a number of years back – perhaps with Mojave or even earlier. I recall a lot of discussion with various discussions blaming Google for making changes and others blaming Apple – in the end, from my perspective the culprit seemed to be Google but neither company ever commented that I saw.
The symptom is that I'm told to re-enter passwords for linked Gmail accounts, which then does the "we need to authenticate via Safari" thing, I enter the correct password but the confirmation is never passed back from Google.
Anyone else seeing this?