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You have the correct prod keys 21, but you are missing the firmware files . Fix: Ryujinx needs the actual decrypted firmware to run system processes. Download Firmware 21.0.0 (as .nca files) and install it via Tools > Install Firmware in Ryujinx. Prod keys decrypt the firmware; the firmware runs the game. ryujinx prod keys 21
For developers and power users, the strict key handling of Ryujinx is preferable because it surfaces issues early. This is precisely why the search term “ryujinx