As many others have, I’ve struggled with the intense rudder issues related to using an XBox controller. In my case, it is with a PS4 controller (masquerading as an XBox controller via DS4Windows.)
I had success with a workaround to bypass the issue of being able to map the RT/LT to the rudder axis. DS4Windows allows you to map any control input to any virtual XBox Controller input you like, so essentially I swapped the controls for L2/R2 with RS left & right. MSFS2020 let me set the <-RS-> as the rudder axis, and LT/RT as look left/right, effectively keeping my control input the same, but with vastly improved rudder control.
(If you didn’t follow all that mapping, basically, when I press L2 on my controller, MSFS thinks I pressed left on the RS. And when I press left on the RS, it thinks I just pressed L2, etc.)
I flew around performing slips and steep turns on a point, and was able to do 360 turns staying within 20’ of my starting altitude, which would have been impossible with the default rudder configuration without the rudder twitching/glitching out and causing the plane to violently rip into a steep bank/dive in the direction of the rudder input. I no longer have to hold both trigger buttons simultaneously to get smooth rudder control on the ground (or do the TAP TAP TAP rudder input) on take off/landing.
I imagine there’s got to be a way to accomplish this same kind of input remapping via software for those using actual XBox controllers, but I don’t have any lying around to test out.
Anyway, I hope this helps a few people out while we wait for the devs to implement the ability to directly map LT/RT as the rudder axis. (Please devs!)