SERIAL_5 as a general-purpose port on Pixhawk Cube?

Hello.

I am thinking about making a custom carrier board for the Cube Black. The SERIAL_5 port seems to be dedicated to the NuttX system console but I would like to use it as a general-purpose serial port (for MAVLink messages).

After a request by @proficnc, ArduPilot pull request #6761 enables general-purpose use of the SERIAL_5 port on FMUv2 and FMUv3 so there shouldn’t be any hardware issues with making this work.

So my question is: can the SERIAL_5 port be used as a general-purpose port on the Cube Black running PX4? If not, would it be difficult to implement this functionality?

According to the Serial Port Configuration and Parameter Reference pages of the PX4 documentation, it looks like SERIAL_5 is not configurable but I wanted to ask here to be sure.

Regards, Gudmundur

I could probably also go with the Cube Yellow or Cube Orange, if that changes anything.