Now that I think about it, it's pretty shocking if a trainer doesn't support FTMS - did you check if it does? Possibly they are programming the Microchip BLE ga

Now that I think about it, it's pretty shocking if a trainer doesn't support FTMS - did you check if it does? Possibly they are programming the Microchip BLE gateway to implement the necessary FTMS characteristics and using the UART bit for talking to the app.