This external simulator for AgOpenGPS could probably be modified to this use quite easily: External simulator using a game engine (Godot) . Currently it outputs only $PAOGI-message, but modifying it to output NMEA should be easy. For serial port support this would need some twiddling because Godot engine doesn’t support them by “out of the box”. Very quick search led to this module that could handle that aspect, though: GitHub - matrixant/serial_port: A godot module support serial port communication.