This mod requires Forge and I do not plan to create a Fabric version.
With JRFTL you can convert Rotten Flesh to Leather. By Default, leather is created by smelting rotten flesh. However, when the HardMode is enabled in the config file, first a prepared flesh has to be crafted from 4 rotten flesh and then smelted in a furnace.
With version 1.2 and newer you can also smelt leather in a smoker (twice as fast).
You are free to use it in any Modpack, if you Link this Curseforge page for modpacks, that are not hosted on Curseforge.