The following is provided in the event your Google mail account in Thunderbird stops working when UMass IT changes the available authentication mechanisms on January 12, 2022. (Unfortunately, there is no guarantee that Thunderbird will continue to work with your account after the 12th.)
The following was done on a Mac, but it looks and works the same on Windows.
You get to the screen below within Thunderbird by going to the three horizontal lines in the upper right > Account Settings > Account Actions (lower left) > Add Mail Account.