A chicken farm. Fully automatic. A bonemeal-less crop farm. A bed A clock A storage system. A shulker box loader will help. A furnace and an enchanting table. Not strictly resource-less (they use coal and lapis), but they won’t be used very often. An ender pearl station. Again, not strictly resource-less, but won’t be used often. An under-floor armory.
A small tree farm, to provide wood and charcoal A charcoal smelter. A backup nether portal, as an emergency exit. Rooms for more people. If you are near one, a skeleton spawner farm. With this providing bonemeal and XP, you can make all your other farms more compact. Melon, pumpkin, sugar and cocoa bean farms. Whatever else you can imagine. At this point, it’s becoming less of an underground bunker and more of an underground city!
