Updates with more issues and the solution.
TLDR;
Remove Warsaw DLLs. Search for Warsaw or Topaz on your programs and uninstall. There’s a high chance you have them if you live in Brazil. Downside: you won’t be able to use your computer for online banking.
The whole problem was cooking. My cooking time was very short: 1s. I tried to cook with the command line only, and realized that running the 5.6 binary UnrealEditor-Cmd.exe without any arguments was throwing a exception. The same binary for 5.5 opens the editor.
The exception is never thrown on regular cooking inside Unreal Engine because it has a flag -unattended, which suppress pop-up dialogs. That’s why it took me so long to pinpoint the cause.
So, by just running the binary below:
C:\Program Files\Epic Games\UE_5.6\Engine\Binaries\Win64\UnrealEditor-Cmd.exe
Generates the exception on a crash pop-up:
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x00007ffebab430a7
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Core
UnrealEditor_Cmd
UnrealEditor_Cmd
UnrealEditor_Cmd
UnrealEditor_Cmd
UnrealEditor_Cmd
UnrealEditor_Cmd
kernel32
ntdll
This also generates a dump that you can find on the GUI that appears when the exception is thrown. There are 2 DLLs with paths Topaz OFD\Warsaw. These are the culprits. They’re common here in Brazil. We need to install them for bank applications and they cause a lot of issues (including this one). After I uninstalled it, the cooking started to work just fine.
Disclaimer: It was luck, I saw them listed and decided to uninstall to see what was going to happen.