Shulkers normally are the only remaining option for mob switches (Mojang, please do not remove ), as they don't despawn but count toward the mob cap. In order to make my mobswitch look nice and not have shulkers teleport everywhere, I put them in a minecart to also easily swap them between chunk borders. On my realm, my updating to 1.16 will break not only my farms but the mobswitch that would let me repair them without being flooded with items. This screenshot shows a singleplayer world with two shulkers in a glass flat world I just emptied of entities, one in a minecart and one not. Both were spawned with a spawn egg, no commands other than to kill everything. The new mob cap display shows not 2 for monsters, but 1. The other screenshot is my mobswitch, and I can't prove that it works with the f3 screen, but there are no hostiles when the light is on, and when it is off mobs can spawn when you are far enough away.