There’s been a lot of talk (consternation, wailing, gnashing of teeth) over the fact that the CP2102 seems to be the only USB serial adapter that works natively with Win10 IoT core. Of course, I have a small mountain of unsupported FTDI adapters.
I am happy to report that if you also have piles of Arduino stuff, you may be in luck. I’ve found that the Arduino USB Serial Light (https://www.arduino.cc/en/Main/USBSerial) also seems to work with Win 10 IoT Core on the Raspberry Pi.
Word of warning - the output from the Arduino adapter is 5V TTL serial.