My client has an auto attendant which sends calls to a queue that rings his desk phone. However, the queue also needs to activate an external ringer in case he's out in the field. I currently have such a ringer on a VoIP ATA (It is a Grandstream HT801) that is connected via SIP to another provider. To get it to ring, I just need to dial its number.
I have set up a Teams user called External Ring with immediate call forwarding enabled to the ringer phone number and joined it to the queue. This user has Office 365 Business Basic and Business Voice licenses. Direct dials to the External Ring user work, but calls from the queue will not ring the forwarded number. Configuring the ringer number for simultaneous ring on my client's user account won't work for the same reason.
From the posts I have seen so far, Teams queues will not ring external numbers defined on user accounts. I've toyed around with using SIP gateway, but it appears to only support a small pool of devices, and I'm not sure I could get the ATA to work with it. Is there some kind of workaround that anyone knows of?