I ferment all kinds of vegetables. My favorites is a perennial tree kale that grows all year around in California. I shred it with a flow-thru shredder and pack it into a crock
(3 T kosher salt per 5 lbs of vegetable matter)

Recently I also have been "krauting" nopales, aka prickly pear cactus pads (ficus opuntia indica). It is an indestructible drought tolerant plant.
(Remove prickers. Cut into small cubes or shred it with a wide blade. Pack as usual. It has nice crunchy consistency.)