The good news is that GtkSharp is the only requirements. The bad news is that GtkSharp requires other libraries:

PS Too fast. It is not the only requirements:

$ find . -type f -exec grep PackageReference {} \;
    <PackageReference Include="GtkSharp" Version="3.24.24.34" />
    <PackageReference Include="NUnit" Version="3.13.2" />
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.0.0" />
    <PackageReference Include="NUnit3TestAdapter" Version="4.1.0" />
    <PackageReference Include="GtkSharp" Version="3.24.24.34" />
    <PackageReference Include="GtkSharp" Version="3.24.24.34" />
    <PackageReference Include="GtkSharp" Version="3.24.24.34" />
    <PackageReference Include="GtkSharp" Version="3.24.24.34" />
    <PackageReference Include="GtkSharp" Version="3.24.24.34" />
    <PackageReference Include="GtkSharp" Version="3.24.24.34" />
    <PackageReference Include="GtkSharp" Version="3.24.24.34" />
    <PackageReference Include="NGettext" Version="0.6.7" />
    <PackageReference Include="SharpZipLib" Version="1.3.3" />
    <PackageReference Include="ParagonClipper" Version="6.4.2" />

BR,

Andrea