Oauth error prevents logging into gmail account
Using Evolution 3.36.3 on Pop!_OS 20.04 trying to connect to a university gmail-based IMAP account, Edit > Accounts > Add Mail Account, provided e-mail address, "Looking up account details...", provided user name, and server imap.gmail.com, no changes to default options, smtp.gmail.com for outgoing server, no changes to next panel, Apply.
Google Mail authentication request window appears. Provide e-mail address, Next, university two-factor authentication, Gnome Evolution wants to access your Google Account, Allow, "Failed to obtain access token from address "https://www.googleapis.com/oauth2/v3/token.": The file was externally modified.", Cancel, Choose an account, click on account name, Gnome Evolution wants to access your Google Account, etc etc.
Google account is set up with two-factor authentication. There are postings saying to deactivate two-factor and click on "allow less secure apps" but that didn't work either. In any case, https://gsuiteupdates.googleblog.com/2019/12/less-secure-apps-oauth-google-username-password-incorrect.html says they will disable this option soon, although they apparently delayed doing so due to the pandemic. I have no problem logging into this account using Thunderbird using the app-specific password option. No such option appears to be available for Evolution. Any assistance would be appreciated.