Legally, you cannot run Ryujinx without owning a Switch and dumping your own BIOS/keys. Emulators themselves are legal, but bypassing encryption without owning the original hardware is a legal gray area that often violates DMCA anti-circumvention provisions.
You also need a title.keys file for DLC and updates. Place it in the same system folder. Many guides bundle these together, but note that modern Ryujinx versions handle title keys differently—they often prefer to read them directly from installed game files. ryujinx prod keys v1800 latest product keys