Chicken bait wither rose farm

The original safe wither rose farm, by Rays Works. A wither is summoned into the bedrock of the End's exit portal, where it cannot move, and a chicken placed just in front gives it something to keep firing at. Bubble columns redirect the skulls so they hit the endermen falling down the drop chute rather than the farm itself, which is what makes this design safe from the rare blue skull that destroys almost anything. Every enderman killed by the wither effect leaves a wither rose. Shulkercraft's wither rose farm is built on this design, and Rays maintains the description with fixes as versions change.

The fall height is what breaks this on newer versions. Endermen die to fall damage before the wither can kill them, so nothing drops. daniq715 takes four blocks off on 1.21.11, reptours and melons123 lower the spawning platform by one on 1.21.10 and 26.1.2.
Use ice for the water sources above the soul sand and break it quickly. netherwhal says the flow comes out predictable that way and no other method does.
Put a two block wall in front of and behind the chicken before the wither blast, then pull both out straight after. The chicken gets shoved out of place and you have to push it back.
Do not bother blast proofing before the summon. netherwhal says the wither only takes out a few blocks and they are easy to replace.
The AFK platform goes 84 blocks above the enderman spawning platform. Any higher and the endermen despawn before they reach the chute.
Wear full armour with a totem and use invisibility for the wither spawn. cjblackwell372 suggests running the whole sequence in creative once first, because a mistake leaves you with a dead chicken and a loose wither.