You can find the plugin on the JetBrains Marketplace:
SumnekoLua Plugin - Stable Version

Intellij-SumnekoLua is a plugin for IntelliJ IDEA that adds comprehensive support for the Lua programming language. Built on top of SumnekoLua (also known as luals), this plugin offers a range of features to enhance your Lua development experience, including:

• Intelligent code completion
• Advanced code navigation
• Automatic code formatting
• Syntax highlighting
• Error detection and quick fixes

Whether you are working on small scripts or large Lua projects, Intellij-SumnekoLua aims to streamline your workflow and improve productivity.

If you encounter any performance issues while using this plugin, we recommend trying Intellij-Emmylua2, which may offer better performance for certain use cases.