Bell module iron farm

A multi module iron farm using bells to keep the villagers reacting, with the zombies hung in boats beside the pods. Golems spawn on the platforms and wash into lava over the hoppers, and the whole thing is built as layers you can stack for more output. Java only, with a separate Bedrock version on the same channel.

The farm stops after the first night because the villagers never sleep again. Put an extra bottom slab and a glass block above the bell, which several builders confirm fixes it.
A second fix for the same problem: raise the zombies by two blocks and add a slab with glass above it, but only in the modules that have bells.
It also breaks whenever the chunks unload or the world reloads, and several builders have to relog to get one more night out of it.
Golems get stuck on the fence gates. Extend the gates out by one block, or replace the gates at the end of the water stream with signs.
Wandering trader llamas kill the zombie in the boat. One builder swapped the hanging boat for a drowned bouncing on a soul sand water column and says that fixed the sleeping problem as well.
If almost nothing spawns, check for caves under the farm before anything else.