CyanogenMod has been the most widely-used custom ROM for years, with at least 10 million users at one point. After Cyanogen Inc kicked the bucket, the community-maintained LineageOS continued CM's efforts. The official statistics page for the project now shows 515,000 active installs (at the time of writing), a great achievement for the relatively-new ROM.
The statistics page has some other interesting information. The most popular device, in terms of active installations, is the OnePlus One (bacon) with 40,000 installs. This is followed by the Redmi Note 3 (kenzo), the OnePlus 3/3T (oneplus3), and the international Samsung Galaxy S3 (i9300).
Since LineageOS is a direct continuation of the CyanogenMod project, it makes sense that the ROM would pick up many of CM's former users - especially with a direct upgrade path. But it's still nice to see that project has achieved a good start, and I wish the developers luck for the future.
- LineageOS Stats