"Not supported" in this case simply means: If you fail over, don't expect consistency. And more importantly: Do not expect support(!)
You can still "just do it", and hope you never run into problems. If you are willing to risk consistency. I would stay away from that, or build an infrastraucture with marked transactions and probably manual failover, that would allow me to use parts of
AlwaysOn (but not all) + distributed transactions.
Andreas Wolter | Microsoft Certified Master SQL Server
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