I am on 8.1, problem is I tried upgrading to windows 10 a year ago. I was one of the "early adopters". I cant remember properly but there was incompatibility with Visual Studio with Xamarin on. I was reliant on developing an app at that time and could not afford downtime, so I reverted back to 8.1.
8.1 still gets updates until 2023. They only mean 8.0 with those packages. :)
They should add a clearer error message when trying to install an 8.0 package though.
I will try upgrading again when I get time.