Due to changes in the code that handles how equipment durability works that happened around the 0.8 updates, this mod is broken. I've attempted to fix it off an on since then, but haven't been able to find a way to make it work. Maybe some day I'll figure it out, but I'm working full time and my wife, who I originally made this mod for, isn't as interested in the game these days.
If you want to take a crack at making it work again feel free to fork, although to be honest, you'd probably be better off writing it from scratch. The original code really only required a one liner to make it work, and having delved deep into the games code base to understand how durability works since the updates, you're gonna need to be smarter than a single line of code.
A small plugin for preventing equipment from taking damage.
This mod requires BepInEx6 to be installed, and should be installed in BepInEx's plugin folder. For information on installing BepInEx for Core Keeper look here https://core-keeper.thunderstore.io/package/BepInEx/BepInExPack_Core_Keeper/