The GPS is correctly connected to UART6 on my MambaF405v2 - when I flash Betaflight to the FC, set UART6 as GPS, 57k baud expecting NMEA I get good GPS fix with 5 sattelites.
When I configure ArduPilot with the same wire connections I set SERIAL3, SERIAL4 and SERIAL5_PROTOCOL to -1
to disable them as nothing is connected here. I then set the necessary parameters for NMEA GPS on 57k baud running on Serial6
In case someone comes across this: I’ve now switched to using a MambaH743v4 and bought a Baitian BN880Q.
The BN880Q works on the MambaH743v4 using the following config: