Hello @gavmacav ,
Welcome to the Poly Community.
The restrictions on how many additional devices are pushed by the providers that are being used.
In regards to MTRoA our partner Microsoft, as the provider in this case, will only allow 1x TC8
You could "theoretically" use a Poly Trio 8800/8500/C60 as a "controller" but it is not a replacement for the TC8 and is more of a remote. Support for this could be withdrawn at any version.
The best and quickest way forward is to contact our Support organization as the community is run by volunteers only.
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
If official support is required please check how to phone or open a case here
The title Poly Employee & Community Manager is a community setting and does not
reflect my role. I am just a simple volunteer in the community like everybody else. All posts and words are my own & do not represent the views of Employer. ----------------
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge.
Please also ensure you always check the VoIP , Video Endpoint , Microsoft Voice , PSTN or other FAQ's in the different sections