In my case, the issue seems to origin from the fact that only player 1 can use hotkeys, but for some reason my controller's driver xarcade2jstick is by default reversing the sides of X-Arcade Tankstick, when retroarch is getting input. As a result, the lift side of the stick, recognized as Controller 1, is controlling player 2 in games and vice versa.
I guess that this prevented the Select as hotkey enabler from working. I made it work by fiddling around with the retroarch settings, and reversed the controllers, and not everything seems to be good.
I had my tankstick configured with the default mapping.
What I ended up doing was just adding these lines to the bottom of /opt/retropie/configs/all/retroarch.cfg and everything worked great after launching another game.
input_player1_joypad_index = "1" input_player2_joypad_index = "0"Here's the mapping I use
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