Portal grid gold farm

A portal spam gold farm on the nether roof, and by common agreement the fastest thing that can be built up there without breaking bedrock. Zombified piglins spawn on a grid of nether portals and teleport to the overworld the moment they appear, where a player kills them with a looting sword and the drops go straight into shulker box loaders. It needs two players, one AFK in the nether on the spawn side and one killing in the overworld, or a carpet mod bot standing in for the first. Java, and the obsidian bill is the biggest of any farm here.

Pinned by the creator: chunk align the nether side so the in chunk coordinate at the AFK spot reads 0 15 0, and work out the overworld side exactly as the video does, using the Targeted Block coordinate from F3. Get that wrong and the portals link somewhere else, which is the most common way this build fails.
It needs two players. A chunk loader is not a substitute, only a player within 128 blocks stops the piglins despawning. A carpet mod bot does the job, and more people AFK on the nether side raises the rate.
Light each portal as you finish its level. Lighting them all afterwards is close to impossible, and you need roughly 27 flint and steel either way.
Since 1.21 some piglins wear thorns armor and hit back. The boosted regeneration beacon linked in the description outheals it, and glass blocks under the fence gates stop the knockback pushing your bot off the armor stand.
In 1.19 endermen spawn on the portals and ruin things. Waterlogged leaves or stairs stop them teleporting in. The 1.20 spawn changes fix it on their own.
Rain puts out the fire that burns the unsorted items. Put a glass block over the fire.