Microsoft Teams: Unified groups aren't supported
Oh dear. Please, tell me what went wrong.
A classic Microsoft error, providing no information to anybody who doesn't have intimate knowledge of the code and a rough idea where the exception may have been risen.
I received this error when trying to configure a Connector in Microsoft Teams for a channel. It turns out that Unified Groups are an Exchange 365 concept, I guess for some form of distribution list. I'm not entirely sure how they relate to configuring access to a Connector in Teams, but they do (not that you have to be explicitly added to one of these groups to fix the error).
It seems to me there is a bug in Teams that does not handle this error well.
Workaround
The solution is to add an Exchange 365 license to the user experiencing the error. You do not have to create a mailbox or use cloudy Exchange, just have the license assigned. Applying licenses seems to take a little while to take affect and a relogin might be required.