Here is what I know about connecting Scribe v3.15 and later to Gmail. Note that you need to set both sending and receiving use the OAUTH2 authentication type.

Install pre-requisites:

• Scribe will need mkcert installed to create a HTTPS certifcate for the localhost redirect that OAUTH2 uses. This will attempt to install a certificate authority in your browser. This will allow the redirect from Gmail back to a localhost server without getting stuck accepting the security of the connection.
  • Windows: download from the releases page and rename the executable to 'mkcert.exe' and put it in the PATH somewhere. I created a folder under 'c:\Program Files'.
  • Linux: 'sudo apt install mkcert'
  • Mac: probably similar to windows?
• Install Openssl.
  • Windows: Download the latest 'Win64 OpenSSL v3.x.x Light' build from here. Keep the default install location of 'C:\Program Files\OpenSSL-Win64'. I also choose to keep the binaries in the 'bin' subfolder not 'C:\Windows'.
  • Linux: apt get it... although I would assume it's installed by default pretty much everywhere.

Configure an account in Scribe to access Gmail:

• From Scribe's main window click File → Options.
• Click the Accounts tab.
• Select the account to be used for Gmail, and click Properties
• In the Identity tab call the account "Gmail" if you want. Add a display name and your gmail address as the email.
• On the Send tab set the fields:
  
• On the Receive tab set the fields:
  
  
• Save your changes with Ok.

Then test the account:

• Open out the Status panel in Scribe
• Click the gmail account, and then the receive log tab.
• Watch the progress and Log window to see if it connects and scans the mailbox.