If a company is using Google’s servers for incoming mail directly (MX record), K-9 Mail should be able to find the server settings automatically. In your case the company might be using some intermediate MX (e.g. for malware detection). In that case you have to manually set up the account. See How do I add a Google Workspace account?
Note: There’s currently an ongoing issue with OAuth (sometimes) being blocked by Google for K-9 Mail. See Yet another issue with Gmail