Starter hoglin farm

A hoglin farm on the nether roof above a crimson forest. The spawning platform is floored with nether wart blocks, which is the idea the whole design rests on: hoglins can walk across them but nothing can spawn on them, so the platform stays clear without spawnproofing it. Warped fungus funnels the hoglins off the edge into lava below and the meat comes out cooked, with leather alongside it. You AFK on a scaffolding tower at the build limit so the farm sits alone inside your spawning sphere. It is one of the cheaper hoglin farms and the rate holds up: builders across four years of versions report it doing what the title says.

The nether wart blocks are the trick. Hoglins path over them and nothing can spawn on them, which is what keeps the platform clear.
Do not substitute warped wart blocks. Piglins and zombified piglins spawn on those. Shroomlights work instead, and torches on the wart blocks fix it if you already used the warped ones.
AFK at the build limit and in the same chunk. Anywhere near the platforms and nothing spawns at all, which is behind almost every report of a dead farm.
6 double chests and 18 hoppers fill faster than you expect. Add storage before you AFK overnight.
It stacks. One builder took it to the height limit in a test world and got about 50,000 an hour.
One builder on 1.21.6 says the spawns stop after 30 to 35 minutes with the mob cap not full. Nobody has explained it.