One of the important features of the PS4 on recent firmwares is the possibility to install games on an external USB disk, which can be useful if your internal drive is lacking space. Unfortunately, for user-created packages on hacked consoles, this feature didn’t work (throwing error CE-41798-9). Tools such as app2usb exist as workarounds to this limitation, but might be considered a bit hard to use for some users (more on this below).
Flatz has provided patches to fix the error, and allow fpkg files to be installed on the PS4’s extended hard drive. The developers of some of the payloads for the 5.05 exploits have already updated their payloads such as XVortex.