Here's a late entry to your options: Get one of the ATU kits that are readily available online, running the software from N7DDC.? Modify the HW, and/or the SW. But you have all of the pieces you need in the kits.
software:
hardware:
just one of MANY available from AMZN:?
Or from AliExpress:?
I've ordered and built the ATU-100's in the past, they work quite well -- I've used them with QRP radios (e.g. QDX from QRP-labs), as well as a k3 with no tuner.?
-Brian N9ADG
