Hi @Mark Visschers ,
The Application Insights SDK does currently support .NET 5.0. The codeless version of Application Insights is not supported on any version of ASP.NET for Linux OS Web Apps. We recommend you to use the SDK if necessary.
Support for .NET 5.0 using Windows Web App will be added in the future but we currently don't have an ETA to share. Until then, please utilize the Application Insights SDK for your blazor app. To stay informed for future releases and product updates please visit the Azure App Service team blog.
Hope that helps.
-Grace