Looking at your sample for exporting data from the Grid control to Excel (or any format for that matter) using packages imported to .NET 6. Can't find any references to the GridExcelConverter
Imported Syncfusion.XlsIO.WinForms, Syncfusion.Grid.Windows, Syncfusion.DataGridExport.WinForms. What am I missing. Do you have a link to a .NET 6 project?