Apparently now, net6.0 projects that consume the library do require referencing System.Text.Json 8.0.3

tests/SharpGLTF.Core.Tests/SharpGLTF.Core.Tests.csproj

@@ -16,7 +16,8 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />    
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
+    <PackageReference Include="System.Text.Json" Version="8.0.3" />
   </ItemGroup>
 
 </Project>

tests/SharpGLTF.Ext.3DTiles.Tests/SharpGLTF.Ext.3DTiles.Tests.csproj

@@ -18,6 +18,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
+    <PackageReference Include="System.Text.Json" Version="8.0.3" />
   </ItemGroup>
   
 </Project>

tests/SharpGLTF.Runtime.Tests/SharpGLTF.Runtime.Tests.csproj

@@ -18,6 +18,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
+    <PackageReference Include="System.Text.Json" Version="8.0.3" />
   </ItemGroup>
 
 </Project>

tests/SharpGLTF.ThirdParty.Tests/SharpGLTF.ThirdParty.Tests.csproj

@@ -15,7 +15,8 @@
     <PackageReference Include="NUnit" Version="4.1.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
-    <PackageReference Include="System.Drawing.Common" Version="8.0.4" />    
+    <PackageReference Include="System.Drawing.Common" Version="8.0.4" />
+    <PackageReference Include="System.Text.Json" Version="8.0.3" />
   </ItemGroup>
 
   <ItemGroup>

tests/SharpGLTF.Toolkit.Tests/SharpGLTF.Toolkit.Tests.csproj

@@ -17,7 +17,8 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />    
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
+    <PackageReference Include="System.Text.Json" Version="8.0.3" />
   </ItemGroup>
 
 </Project>