Kambrik is a general-purpose Kotlin library meant to simplify mod development, so you'll usually install it as a dependency of other mods. It's available for Fabric, Forge and NeoForge on Minecraft 1.17.1 - 1.21.1.
It offers simplified registration of items, blocks and enchantments, a command DSL, a Message API for sending data over the network, reusable extension methods and a text builder DSL, plus experimental Object to NBT conversion via Kotlinx Serialization.
If a mod on your Minecraft server lists Kambrik as a requirement, it's a one-click install from the panel.