While you cannot install "Fake PKGs" (FPKGs) on official firmware, you can manually install (such as official game updates or demos) using IDU (Individual Display Unit) mode :
The PS4 scene is evolving, but slower than previous Sony consoles (like the PS2 and PSP). As the PS5 matures and the PS4 reaches its end-of-life cycle, we may see an explosion in homebrew development. pkg ps4 games
For the homebrew community, PKG files are the standard format for installing custom software, game mods, and backup games. PKG PS4 Games: A Complete Guide to Installation,
If you are looking for official digital PKG downloads without a cost, these are highly recommended: Call of Duty: Warzone : The premier battle royale experience on the platform. : A massive sci-fi "looter-shooter" with deep MMO elements. Brawlhalla If you are looking for official digital PKG