Some PKG files may be encrypted and require a decryption key to install. rpcs3 can handle some types of PKG files directly, but for others, you might need to use tools like pkg_installer or PS3PKG tools outside of rpcs3 to properly prepare them.
: Use tools like Rusty-PSN to find and download official game updates directly from Sony's servers by searching for your game's serial number [4]. rpcs3 pkg games download