This thread is for all posts concerning Lightroom 6. x, whose last update, 6.14, was released in December 2017.
Since Adobe has officially stopped supporting this version, here are the realities of using Lightroom 6.14 today: lightroom 6.14 license key
If the software was previously installed on your machine, the license key may be stored in local registration files: This thread is for all posts concerning Lightroom 6
For photographers absolutely dedicated to a one-time purchase, several robust, modern raw processors bypass the subscription model entirely: whose last update
Always acquire your license legally, either through your existing Adobe account or by purchasing a legitimate, unused, boxed version from a reputable retailer. How to Install and Activate Lightroom 6.14