Unlocking Nostalgia: Everything You Need to Know About the GameCube IPL.bin
Navigate to /GC/[Region]/ (e.g., /GC/USA/, /GC/EUR/, or /GC/JAP/).
Place the file in your Dolphin user directory (usually Documents/Dolphin Emulator/GC/[Region]/ipl.bin).
If you prefer a legal, non-proprietary version for development or testing, there is an Open Source GameCube IPL project on GitHub that aims to recreate the BIOS functionality.