If you are managing other types of conversions (like PS1/PS2 to PS4 PKG), these tools are highly recommended: PS4 PKG Tool
Requires a Linux-bootable USB, the RPCS3 emulator for Linux, and PS3 system firmware. ps3 to ps4 pkg converter exclusive
Direct native conversion of PS3 games into PS4 PKG files is due to the fundamental architectural differences between the PS3's Cell processor and the PS4's x86-64 structure. While there is no "one-click" exclusive converter that allows a PS3 game to run natively as a PS4 app, users with jailbroken consoles can utilize specific homebrew workarounds or official legacy services to play these titles. Methods for Playing PS3 Content on PS4 1. Linux & RPCS3 Emulation (Jailbroken PS4) If you are managing other types of conversions
due to the radical architectural differences between the PS3’s Cell processor and the PS4’s x86-64 hardware Methods for Playing PS3 Content on PS4 1
This success led to a logical, but incorrect, assumption: If we have a PS2 to PS4 PKG converter, surely a PS3 to PS4 PKG converter exists, but it's being kept exclusive.