@meleu Hey, thank you for the steps! The problem as described in that other thread certainly sounds like what's happening with me.
This doesn't seem to solve my problem, unfortunately. Something I did notice - in the RetroArch config file, after I set the Bluetooth controller up as Player 2, it still gives me this:
input_player2_b = "nul"
input_player2_b_btn = "nul"
input_player2_b_axis = "nul"
input_player2_y = "nul"
input_player2_y_btn = "nul"
input_player2_y_axis = "nul"
input_player2_select = "nul"
input_player2_select_btn = "nul"
input_player2_select_axis = "nul"
input_player2_start = "nul"
input_player2_start_btn = "nul"
input_player2_start_axis = "nul"
input_player2_up = "nul"
It also still gives me the same problem if I set the Bluetooth controller as player 1 and then manually edit the input_player1_ button variables to represent the buttons on the Bluetooth controller. Nothing changes.
I wonder if a fresh RetroPie install and configuring via RGUI is necessary, like the last guy did. Any thoughts?