It’s difficult to help you with your Yaapu problem. You should consider posting your issue on the Yaapu Thread and maybe Alex can help.
Where people stumble on the hardware setup is to set the appropriate SERIALx_PROTOCOL to 10 in the Pixhawk. I also see that the Jumper T16 requires JumperTX 2.2.3 or greater and uses the Horus version of Yaapu telemetry. Perhaps it would be easier to first get it working on your Taranis X9D as this would validate the hardware setup on the Pixhawk and the telemetry cable from the Pixhawk serial port to the FrSky receiver. After that, it’s just a setup issue when swapping radios to the Jumper T16.
Cheers!