Multiple availability groups--can each availability group have its own listener? I have created two availability groups containing multiple databases on the same SQL Server instance.  Can I have two different listeners for these two availability groups?
Yes, you can and should create one listener per Availability Group.  This is mentioned in passing in the MS Docs article Configure a listener for an Always On availability group:


  You can create only one listener per availability group through SQL Server. Typically, each availability group requires only one listener.