Atari's port of Asteroids also supported four joysticks. You could play melee, co-op, or team mode, with four players on the screen at once. It was a blast.
I wrote a four player "Tron lightbikes" game that used all four joysticks. But I was just a kid and didn't really know what I was doing, so there was no collision detection - people being out because they ran into a wall was based on the honor system. lol.
https://www.atarimania.com/8bit/files/Asteroids_manual.pdf