The section Read and Write Rich Text Format Documents of this online article of UWP edition of ComponentOne reads: you can use it to convert RTF
Read and Write Rich Text Format Documents
ComponentOne
you can use it to convert RTF
ComponentOne you can use it to convert RTF to HTML and vice versa.
You could convert between HTML and RTF using the RtfFilter library. And you could also get the code sample with this link.
rtfBox.Text = new RtfFilter().ConvertFromDocument(richTextBox.Document);