Do not drop the firmware files here, install them via Ryujinx:

RetroDECK Configurator -> Open Emulator -> Ryujinx -> Tools -> Install Firmware - Select the firmware zipped file

Check the wiki for more information.

Related wiki article can be found here:
https://retrodeck.readthedocs.io/en/latest/wiki_emulator_guides/ryujinx/ryujinx-guide/

The RetroDECK Team