I know this has been covered. I have a Mode 2 Taranis with RETA. The PH requires AETR. I have switched this everywhere I can think of. Mission Planner shows the correct channels are triggering. D16 SBUS. When I power up, the sticks are all wrong. Am I missing a step? This is a copy of the Aero M plane. (Skywalker) with ailerons on one channel.
About a year ago I discovered this guys channel. “Painless360”, he is a Brit and loaded with useful info. This link is for his Taranis Radio series, a very comprehensive series. I think it will help you out.
Peace, Wolf D.