The "K" stands for "Kunde" (Customer/Release version), while a "P" stands for "Production" (factory installed version). Section 2: Why Update Your MMI Firmware?
Platforms like Audizine, Audi-Sport.net, and dedicated navigation forums (like Digital Kaos) often host curated, tested firmware files and activation scripts.
Audi MMI 3G Plus Firmware Update: The Complete Download and Installation Guide