This is BepInEx 5.4.19 pack for Peglin.
BepInEx is a general purpose framework for Unity modding. BepInEx includes tools and libraries to
BepInEx is currently one of the most popular modding tools for Unity on GitHub.
This pack is preconfigured and usable for Peglin modding.
In particular, the changes from base BepInEx releases are:
BepInEx.cfg with console enabled.This is the recommended way to install BepInEx on the game.
If you are installing this manually, do the following
Extract the archive into a folder. Do not extract into the game folder.
Move the contents of BepInExPack_Peglin folder into <Steam Location>\steamapps\common\Peglin.
Check that you have installed it correctly. If done correctly, your folder will look as follows

Follow either Windows or macOS game running instructions below:
No need to configure. Simply run the game. If everything is correct, you will see a console pop up.
Make run_bepinex.sh executable with chmod u+x run_bepinex.sh.
In Steam, go to game's properties and set game's launch arguments to
<pwd>/run_bepinex.sh %command%
Where <pwd> is the path to the game's .app
Run the game via Steam.
At this moment you will not see any clear indication if BepInEx works. It is suggested to test by installing a simple plugin such as MessageCenter from BepInEx.Utility.
At this moment, you can use the following channels to ask for help