MahApps.Metro: Can't build 1.6.5 in VS2019

I tried:

1. Only the .NET Core SDK from the build instructions is installed.

2. Checkout 1.6.5 (cb9264828def32d2c55ec32dc0426c8a72aa793d)

3. Run .\.paket\paket.exe restore

4. Rebuild twice in Visual Studio

   I get:

   1>Properties\AssemblyInfo.cs(7,12,7,21): error CS0246: The type or namespace name 'ThemeInfoAttribute' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(7,12,7,21): error CS0246: The type or namespace name 'ThemeInfo' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(9,12,9,23): error CS0246: The type or namespace name 'XmlnsPrefixAttribute' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(9,12,9,23): error CS0246: The type or namespace name 'XmlnsPrefix' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(10,12,10,23): error CS0246: The type or namespace name 'XmlnsPrefixAttribute' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(10,12,10,23): error CS0246: The type or namespace name 'XmlnsPrefix' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(12,12,12,27): error CS0246: The type or namespace name 'XmlnsDefinitionAttribute' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(12,12,12,27): error CS0246: The type or namespace name 'XmlnsDefinition' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(13,12,13,27): error CS0246: The type or namespace name 'XmlnsDefinitionAttribute' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(13,12,13,27): error CS0246: The type or namespace name 'XmlnsDefinition' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(14,12,14,27): error CS0246: The type or namespace name 'XmlnsDefinitionAttribute' could not be found (are you missing a using directive or an assembly reference?)
   1>Properties\AssemblyInfo.cs(14,12,14,27): error CS0246: The type or namespace name 'XmlnsDefinition' could not be found (are you missing a using directive or an assembly reference?)
   
   ...14000 more errors...
   

5. .\build.ps1

   I get:

   MahApps.Metro\src\MahApps.Metro.sln.metaproj : error MSB4057: The target "restore" does not exist in the project.
   

I’m running VS 16.2.3.

Any ideas?