I've never used 2FA for Gmail but if you do, it's apparently a setting you can toggle off/on via a Gmail web login or presumably in their app (I've never used that). Despite reports to the contrary, it's working fine with no annoying 2FA (two-factor authentication, where you have to get a code via text every time you check or send email). Now I'm able to login automatically in Tbird Ubuntu and keep using POP for local storage.

Now it seems clear the only requirements are the latest Tbird version, and OAuth2 login rather than password. At first I thought Google will now demand IMAP, so I wasted time trying to find out how to set that up so new email could still be stored on my computer. I have email going back to the 1990s stored in mailboxes on my computer and want to keep using Gmail that way. They grumbled about ' insecure access' but I couldn't find any clear guidance on exactly what they will require (especially for POP/SMTP), what my options are, or exactly how to proceed. Lately I've been getting dire warnings from Google that my POP SMTP Gmail accounts won't work on Thunderbird ( aka Tbird) after the end of May 2022.

Configure thunderbird for gmail