There are third-party tools and scripts available online that claim to unlock DLCs. Examples include tools like "CK2 Unlocker" or similar. , as they may contain malware or violate Steam's terms.
Some users have created third-party tools, like the "Crusader Kings 2 All DLC Unlocker," which claim to unlock all DLCs. , as they might: crusader kings 2 all dlc unlocker