Hi Peter\Del Woodcock,
Thank you for contacting Syncfusion support.
We can reproduce this issue while .NET6.0 SDK only installed. We are not yet provided .net6.0 support to Syncfusion Blazor template Studio. Already, we logged this as feature request and will update on our upcoming Essential Studio 2021 Volume 4 release. You can track below feedback link for further about net6.0 support for Syncfusion Blazor Template Studio.
As of now, please install .net5.0 SDK and create a net5.0 sample from Syncfusion Blazor Template Studio if you want. We will update further details about net6.0 support on above feedback link.
Please let us know if you have any other assistance.
Regards,
Abishake Dakshinamoorthy