It is easy to say the Duo is a smartphone but when you look at how Microsoft is promoting the hardware, to me, this is device reminds me more of the PDAs of the early 2000s than of the smartphones of the 2020 era.
Brad Sams' review of the Microsoft Duo is the first I’ve seen that calls it a Personal Digital Assistant (PDA), which I suspect is a better categorization than smartphone or tablet. The problem again comes back to price, it’s just way too expensive and doesn’t not provide enough for that expensive beyond being a niche product. My hope is that Microsoft and Google don’t give up on it too soon and find a way to get the price down.