I was trying to run Pico8 with joystick on linux and wasn't being able to.

Until I saw this reddit post: https://www.reddit.com/r/EmuDeck/comments/17dohf8/comment/kspg7o8/

The fact that he was using a steam deck made me think our issues could be related. I then checked the config.txt and the following line:

// Specify which player index joystick control begins at (0..7)
joystick_index 1

Was defaulting joystick's behavior to player 2 instead of 1, even though the index is stated to start at 0 on the comment.

I then changed to this

// Specify which player index joystick control begins at (0..7)
joystick_index 0

And now I can get it to work. Maybe the default behavior was supposed to be joystick to player 1?

see also the new merge_joysticks setting: https://www.lexaloffle.com/bbs/?tid=140421