In the PlayStation 2 homebrew scene, ul.cfg is a critical configuration file used by loaders like Open PS2 Loader (OPL) and USB Advance to index and run games from a USB drive. This file is specifically required when games have been "split" into smaller chunks to bypass the 4GB file size limit of FAT32-formatted storage. Understanding the Role of ul.cfg

xadrianzetx/ulmake: Create and manage PlayStation ... - GitHub

Splitting Games: Tools like USBUtil take a large ISO and split it into 1GB chunks (named ul.XXXXXXXX.00, ul.XXXXXXXX.01, etc.).

start_sector, game_name_in_ASCII, game_id

USBUtil: The most common tool for converting ISOs into the split "USBExtreme" format. It automatically creates and updates the ul.cfg file as you add games.

How to Fix "No Games Found" Error (Ul.cfg Corruption)

You have the file, but OPL says "No Games." Here is the repair guide.