The Telerik.Documents.Spreadsheet NuGet packages should be installed in your project to recognize the Workbook. The illustrated Telerik.UI.for.Maui NuGet package doesn't contain the required package. Only Telerik.Documents.Fixed is included out-of-the-box:
Then, the Workbook is expected to be recognized with the necessary using:
I have attached my sample project for your reference.
I hope this information helps. If you need any further assistance please don't hesitate to contact me.
Regards,
Dess | Tech Support Engineer, Principal
Progress Telerik