How to fix 'Can't connect to the account Gmail' error in Mail after Sequoia 15.4 update?

Google may require that you generate a specific app password to be able to access Gmail from the Apple Mail app. This typically shows up as error with using your Google account password, instead of the app password.

To generate a Google app-password, go here: https://security.google.com/settings/security/apppasswords

Michael Stiebel wrote:

I updated 3 days ago to Sequoia 15.4. The result is that Mail has somehow messed up my outgoing mail settings. I have re-entered these but for some weird reason I get a window which says "Can't connect to the account Gmail" and when I enter the (correct) password, it says it cannot verify this password. Hmm. This happened to me years ago and there was a hack I could use either with my iphone or on a browser window which somehow sorted the issue but it was really a long long time ago.....anybody know how to sort this? Am going nuts here.

[Re-Titled by Moderator]

Suggest reaching out to gmail support on this issue.