I basically got the same error as this post from 3 years ago: Xamarin Android Build Failed "Invalid value for outputAssembly" but I don't understand the solution and was looking for help.
After not changing any code in my master branch, today in VS2019 and Xamarin.Forms 4.4.0.991477, I went to build my app in android, when I got this error
obj\Debug\...\Appname.Droid.dll is an invalid value for the
"OutputAssembly" parameter of the "Csc" task. Multiple items
cannot be passed into a parameter of type
"Microsoft.Build.Framework.ITaskItem".
Now I don't understand the solution from the previous post,
You have to set your Project Linking to Sdk Assemblies Only and set support architecture to armeabi - v7 and x86. After try to clean and rebuild the project
I don't really understand how to go about doing this, where do I go in VS to access these settings? And also is this the best answer in 2020, or is there another one? Thanks!