0) Enable UART port you want to use in system.fex / build serial-usb modules or build into kernel for USB
1) Install SuperSU (might not be required YOMMV)
2) connect GPS
3) Install https://github.com/HvB/UsbGps4Droid/downloads
4) Configure said app and start it
If it can save someone else's the trouble of trying to the the GPS sources to work, figured it'll be at least that...
DW