We should consider simplifying retrieving access token for SharePoint by using sharepoint as a resource rather than the exact SharePoint URL. If SharePoint URL has been previously retrieved (this can be confirmed using m365 spo get), you could specify m365 util accesstoken get -r sharepoint and the command would replace sharepoint with the actual SharePoint URL and return the token. If the SharePoint URL hasn't been established, the command would fail with an error asking you to specify a valid URL.

This adjustment would make a shorthand for retrieving SharePoint URL and free you from having to memorize the exact SharePoint URL which is extra inconvenient if you use CLI to work with multiple tenants.