My fault.
Answer for the issue I've posted on Github:
".NET 6 is out of support. The 9.0.0 version of that package dropped the .NET 6 target framework, so when you upgraded to the 9.0.0 version of the package, you started getting the .NET Standard implementation. ... The recommended solution would be to move your project to .NET 8.0 or .NET 9.0, or alternatively stay on the 8.0.0 version of the package."