1.17 Single-Dimension Shulker Farm (Any Dimension, Self-Sustaining)
Channel: teh3l3m3nts Minecraft Server
Date: 2021-05-10

This is my design, built in Snapshot 21w18a, for a single-dimension Shulker farm which can technically be built in any dimension (specifically The End, but also the Nether if you replace the snow golems with a player).  The advantage here is you don't have to relocate Shulkers to the overworld from an end city if you build it there, or this will work if you have a reason to avoid multi-dimensional farms (multiworld plugin, portal linking issues, etc).  This uses minecarts to get Shulkers out of the 17x17x17 spawnable space around the initial Shulker, then compresses and sorts them to keep 5-6 in reserve, then killing any extras.  

The killing chamber was inspired by ilmango and cubicmetre:

ilmango: https://www.youtube.com/watch?v=8RqWiEJuauQ
Cubicmetre: https://www.youtube.com/watch?v=Tv7uVHM43Bw

Detecting the Shulker and making sure it had not teleported out required a very long redstone signal, as the snow golems often lose their attention when the Shulker duplicates and it takes 3-8 seconds for them to target the close one again.  I used ilmango's variable-duration reset-able pulse extender for this with a 22-24 second duration (2 items) for a very safe buffer; if the signal goes out, there is a very good chance the shulker has teleported away.

https://www.youtube.com/watch?v=YlH7lWKa4cI

When Litematica is out for this snapshot I will make a schematic available, for now here is the world download: 
http://www.teh3l3m3nts.com/WorldDownload.ShulkerTest1.zip