Mobs which used to drop leather, now drop hide which has to get prepared with sugar and dried at the wood rack to get leather now.
Rottenflesh can be combined to rotten leather which can get dried to get hide.
This mod is developed for Fabric.
There are no plans to develop a Forge version.
Modpack Permission:
Feel free to use it in any modpacks.
Bug Report:
Just report bugs at the github page.