Making GIFs on a Linux computer requires you to jump through a few hoops, after a few hours of experimentation, this is my solution. Of course, you can also use an online service.

ffmpeg -ss [start] -i input.mp4 -t [duration] -vf scale=280:-1 -r 15 -f image2pipe -vcodec ppm - | convert -delay 5 -loop 0 - output.gif

The time should be set in the following format: hh:mm:ss for example, 00:12:31.