Not sure about relevance I had same problem with Ubuntu Gmail was fine with Thunderbird until it would (supposedly) not verify username & password. I think they dont like VPN,s..sorry well I do. In my case I opened up a new email account in thunderbird & changed settings from POP to IMAP & now its working fine
As for workaround, I've installed Dashlane (a password manager app) where you can automatically import all Google-stored passwords (it should ask on the first run), then using their app you can export them into archive file (such as CSV, Excel or encrypted format). Using this method, I've moved all my passwords from Google Passwords, and never used it again.
Go to myaccount.google.com/security (or security.google.com).
Click the 2-Step Verification option.
You'll probably be prompted for your password to verify it's you.
Scroll to the bottom to Devices you trust. Choose "Revoke all". (Unfortunately, you can't change them piecemeal.)
Now you'll be prompted for the "second step" wherever you're trying to sign ...