Hi @kevon, and welcome to the Auth0 Community!
Unfortunately, we don’t currently have a sample app for .NET 9. I highly recommend submitting a request for it by following this Knowledge Article. I’m convinced that there will be one in the future, and this could help expedite the process!
In the meantime, I will leave you with the Blazor .NET 9 authentication and authorization doc page, and hopefully, you will find the information you need.
Have a great day!
Teodor.