@zitronen
Did some testing on windows 10 because I was bored.
I purchased two Unos that use the WCH340 chip, they both work perfectly. Reading over the entire thread I saw a mention of using a proxy app to receive UDP from KSP and relay that out the serial port using System.IO.Ports. I gave that a shot, but again it fails with the Uno using the Atmel 8u2, but works great with the WCH340 chips.
The WCH340 chips keep on working as long as I keep the UDP listening, but the ATmel chip always hangs up on the serial port methods before reaching an AP of 500m, so it doesn't fail right away, but I can't make it work.