Error APPX0002 after upgrading from UWP to WinUI3

[Siyh]

I have an app that I upgraded from UWP to WinUI3 using this tool. After tackling all the compiler errors and attempting to build I get:
Error APPX0002 Task 'WinAppSdkGenerateAppxManifest' failed. Object reference not set to an instance of an object.
Which is linked to line 901 of:
C:\Users[user].nuget\packages\microsoft.windowsappsdk\1.1.3\buildTransitive\Microsoft.Build.Msix.Packaging.targets

I'm able to build other WinUI3 apps with no issue, so I'm not sure what aspect of upgrade is causing the issue or how to narrow it down. Does anyone have any suggestions?

[Siyh]

After comparing with a WinUI3 template, I found that I needed to add:
<Capabilities> <rescap:Capability Name="runFullTrust" /> </Capabilities>
with
xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"
To the Package.appxmanifest file.