According to the following log provided by a user: https://pastebin.com/GWbfFLxz

This line: https://github.com/yungnickyoung/YUNGs-Better-Caves/blob/1.16/src/main/java/com/yungnickyoung/minecraft/bettercaves/init/BCFeature.java#L32

and many others, use Registry.register, which is unsupported in Forge.

Maybe event.register would work, but again, i do not have the time to look into this.

• Curle, Forge Triage

Duplicate of #82