Shulker Farms
Shulker farms are slightly modified on VanillaX due to Paper servers causing a few issues with Shulker behavior. Due to this, designs often have to be altered to work effectively and be unbreakable.
Automatic Shulker Farm
Minecraft Fast & Simple Shulker Farm | Java 1.17 - 1.21+ | by Balllight & The Archivists - YouTube
You must use the schematic below since it's slightly altered from the tutorial, however this showcase is important to watch.
The Archivists Shulker Farm V4
Shulker farms work through the mechanic where if a Shulker is hit by a Shulker bullet, it has a chance to duplicate itself and teleport elsewhere. The changes made to this farm manipulate those properties to create a safe chamber in the event your original Shulker accidentally dies, which has a low chance of happening but is not impossible.
In the event your main Shulker does die, simply flick the lever and your safety Shulkers will be released into the farm, replacing the original Shulker.
Once your safety Shulkers are released into the farm, ensure to flick the lever back down.