Victoria 2 DLC Unlocker" typically refers to tools like Koalageddon

PATCH NOTES v.1.0 – THE UNLOCKER

Functionality: It bypasses the "paywall" for content already installed on your machine or allows the game to recognize manually added DLC files.

Because Victoria 2 is effectively unplayable without its two major expansions—which fix critical bugs and population mechanics—many veterans suggest skipping complex unlockers.