Copy/Paste from Textview to Mail App Composer not working - MacCatalyst

Can you explain how you are putting the data on the pasteboard? Are you relying on UITextView to do the job for you, or do you have some code that does it?

In the MacCatalyst, Whenever the user copy something with ctrl + c key commands, data is sent to pasteboard by its own method

func copy() 

method. Even overriding copy() method isn't helping.

Where does your code above (i.e.)

[NSAttributedString.DocumentAttributeKey: Any] = [
  .documentType: NSAttributedString.DocumentType.rtfd,
  .characterEncoding: String.Encoding.utf8 
]  

appear in your program, and how is it being called?

Using this code to convert Attributed string into Data for making a pasteboard item.

extension NSAttributedString {
    var convertToData: Data? {
        let options: [NSAttributedString.DocumentAttributeKey: Any] = [
            .documentType: NSAttributedString.DocumentType.rtfd,
            .characterEncoding: String.Encoding.utf8 ]

        let range = NSRange(location: 0, length: length)

        return try? data(from: range, documentAttributes: options)
    }