We will focus on Beetle Saturn (the software renderer) and Beetle Saturn HW (the hardware renderer using Vulkan/OpenGL), as they are the most accurate and widely used today.
By default, RetroArch looks for BIOS files in its system directory. RetroArch/system/ Android: storage/emulated/0/RetroArch/system/ sega saturn bios retroarch
Emulators work by replicating the console's hardware in software, but they cannot legally replicate the proprietary code inside the BIOS chips. Therefore, to get an accurate experience, the emulator needs you to supply that firmware file yourself. We will focus on Beetle Saturn (the software