As of .NET 6, the System.Drawing.Common is supported on Windows only: https://docs.microsoft.com/en-us/dotnet/core/compatibility/core-libraries/6.0/system-drawing-common-windows-only
Since the Telerik.Web.Captcha NuGet package depends on the System.Drawing.Imaging, we should consider migrating to an implementation that does not depend on the System.Drawing
when check your samples, especially your event sample, I noticed, that there is no event and no reaction when try get sound of the captcha on ipad or iPhone.