ShingenPizza
hi, it may not be a bug on your side, but something within the new Steam Controller, but i'm reporting it just in case anyway.
STR
  1. open VRChat
  2. grab and turn on your new Steam Controller
  3. press and hold LB and RB to show the gesture-choosing pop-ups
  4. use both thumbsticks to select different gestures for left and right hand at the same time
what should've happened, and what does happen correctly on my "Xbox Series Controller":
  1. each hand's gesture should be selected independently
what does happen with the new Steam Controller:
  1. both hand's gestures are set to the last gesture selected (among both of the sides collectively)
to be CLEAR: if you select one side first, let go of the thumbstick, and select the other side 2nd, it works fine.
it only breaks when you are actively pushing the thumbstick to select a gesture on one hand, and then push the thumbstick of the other - then the chosen gesture of the first hand changes to whatever the other hand selected.
i have not changed anything with the Steam's controller setup, i even restarted the computer after installing its drivers and updating it, and it still happens.