For total conversion mods (like TNO or Kaiserreich):
Enter the world of cracked versions. For players unwilling or unable to pay the premium for Paradox’s extensive DLC library, cracked versions of HOI4 offer a backdoor. However, they also present a unique technical challenge: The Steam Workshop—the central hub of HOI4 modding—is designed to lock non-steam users out. how to install mods for cracked hoi4
If you’re interested in the game, I’d encourage you to purchase a legitimate copy (often available on sale). The official version supports mods easily through the Steam Workshop, receives updates, and ensures you’re supporting the developers who maintain the game. For total conversion mods (like TNO or Kaiserreich):