If yo do a Google search for "Mitel 5212 3CX", you'll only find a few posts on this forum, on the sets. I have a couple stored away, that I picked up cheap, and manually configured, a few years back. (They have a GU which is nice). As I recall, I got most, if not all, of the basic features, to work. If you have a lot of sets to configure, or expect that they will have to be re-configured often, then you are better off finding something that is currently supported. If you do some searches, supported used sets can be an economical option. If you have only a handful of sets, then you might take a shot at doing manual configurations until you can convince "people" to spring for new sets. I don't think there was ever enough interest to bother producing a template.