I have the K3s and I use the USB interface from the KIO3B (Audio/Digital I/O). This interface acts like a USB to-Serial Adapter USB Audio Codec and supplies a microphone input, speaker output and a USB Serial Port (i.e. COM1)… making the process quite simple... needing only the USB cable. So if you change to this setup, I can help (with documents, suggestions and explanations) since I just successfully connected to Fldigi to K3s using Windows 10. Howard 4x1zz