If you have a modded PS3 and dumped the entire flash and dev_flash folders directly from your console, you technically have the firmware. However, installing the official .PUP via RPCS3 is still the recommended method because it ensures the emulator has the correct file structure and decompresses necessary modules automatically.
Usually, this means you accidentally downloaded the "Web Installer" or a webpage shortcut instead of the actual file. rpcs3 firmware
Emulation isn’t just about silicon. Sometimes, it’s about respecting the software that made the hardware sing. If you have a modded PS3 and dumped