The lion kingdom got to discovering the /opt/google/earth/pro/resources/flightsim/ directory.  That has ini files for configuring the flight simulator.  flightsim.ini  needs to point to controller/thrustmaster.ini in its configurations section.

/opt/google/earth/pro/resources/flightsim/controller has ini files for different joysticks.  generic.ini needs to be copied to thrustmaster.ini Then its controllers_supported section needs a regular expression which identifies the iProduct name in lsusb -v.  This is not to be confused with the iManufacturer shown in lsusb.  The lion kingdom tried iProducts of *Flight*Hotas* & *Thrust*

Goog earth uses a direct libusb connection to the USB device, rather than the /dev/input tree or any XInput method.  It finds the USB device with the iProducts name in thrustmaster.ini.  Since the USB device is automatically claimed by the kernel's HID driver, you need to release the kernel driver with a home made libusb program that calls libusb_detach_kernel_driver.

Helas, none of these steps got the goog to detect the joystick.  Corrupting flightsim.ini by removing the controller/thrustmaster.ini entry made it fail, but deleting or corrupting the controller/thrustmaster.ini file had no effect.

Based on the flightsim.ini file, the game controller support is a future feature that was never implemented.  Someone spent a lot of time making the joystick files in /opt/google/earth/pro/resources/flightsim/controller but none of them were ever used.  It's like a big company where everyone has 1 job, regardless of it ever being used.

An anomaly in flightsim.ini was a different controller/.ini file being specified for each airplane, yet the dialog box in goog earth shows a common joystick option for both airplanes.  Goog earth doesn't even link libusb.so

Since the last major update of Goog Earth, 10 years ago, no-one really uses it anymore.  The very idea of plotting GPS coordinates on a map has gone away like a pair of VR goggles.  The lion kingdom always knew the Ryzen was going to be a return to dual booting Windows.  This might be the 1st need for native Windows in 15 years. 

The only other idea is making the joystick generate the keypress events required to match its analog position & hope the goog doesn't drop any keypress events.