BetaFlight
BetaFlight has basic GNSS support (primarily for OSD and RTH on fixed wing).

1. Wiring
Connect TX/RX to a free UART
Magnetometer is typically unused unless you’re running iNav or special builds
2. Enable GPS Feature
Connect via USB and use the CLI:
feature GPS
set gps_provider = UBLOX
set gps_baudrate = 115200
save
3. Verify in OSD
Enable GPS coordinates, sats, and speed in the OSD tab.