Problems starting sample application with new VS17 project structure

[DevSnobo]

Hello there,

I have been trying for a while to get a simple GTK# + Xamarin.Forms app running, but am still failing to do so.

I'm running Arch Linux and Jetbrains Rider. The gtk-sharp package was installed via pacman and the libs are present.

I took the sample provided in this repo and noticed the old project structure, so I created a new .NET Core 3.1 App project in the solution. Then I added the Xamarin.Forms project, the NuGet packages (Xamarin.Forms, Xamarin.Forms.Platform.GTK) and also the gtk-sharp libs (from /usr/lib/mono/gtk-sharp-3.0; atk-sharp, cairo-sharp, gdk-sharp, gio-sharp, glib-sharp, gtk-dotnet, gtk-sharp, pango-sharp) as dependencies. I also copy over the existing Program.cs file.
At this point, everything needed should be added. So I go ahead and build&run.

The result is:
"Unhandled exception. System.TypeLoadException: Declaration referenced in a method implementation cannot be a final method. Type: 'Xamarin.Forms.Platform.GTK.FormsWindow'. Assembly: 'Xamarin.Forms.Platform.GTK, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null'."

I am an absolute newbie with regards to GTK# and Xamarin.Forms and would appreciate any help. Thanks!