Big Sur: Mail shows no windows after having tried to install Gmail account

I tried to install Gmail on Mail. Not only I did'nt succeed, but since that moment, my regular email account (with a local Imap provider) does not longer appear to work.

The Mail app opens, the dock icon shows a dot under the Icon, the menu bar is visible but does not show a window. A click on "New window" does nothing, nor does "Show all windows". Still new mails comes in (I hear the beep) and the number appears under the Icon.

I already restarted the app, restarted the computer, without results.

Is there a way to re-install Mail?

Following is a EtreCheck file.

Many thanks in advance for your help!