I had an issue with getting my gamepad recognized by Towerfall on Linux, but got some help from Ethan, so now I'll just share this information here in case it helps anyone else. (:

https://wiki.archlinux.org/index.php/Gamepad#Joystick_not_working_in_FNA.2FSDL_based_games

I'm using an iBuffalo Classic USB Gamepad (BSGP815GY) and a USB keyboard- I use them both for 2-player and it works great. The iBuffalo shoulder buttons don't seem to do anything, tho I may just not have it set up right. The keyboard works as expected. On the keyboard I remapped the arrows to IJKL and moved the left-hand cluster up into the home row so it's more comfortable to play on my laptop.

Update: meant to reply to a different question sorry, derp. How do I delete a post?