LineageOS is the most popular custom ROM by far, and the project continues to update more devices to version 15.1 (based on Android 8.1 Oreo). Last time we covered LineageOS, the OnePlus 2, Pixel C, and Nexus 6 received Oreo. Since then, several more devices have been updated, including Google's flagship phone from 2012.
The Le Max 2 (x2), Motorola Moto Z (griffin), and Xiaomi Mi Note 2 (scorpio) already have 15.1 nighties available. The Xiaomi Mi 6 (sagit), along with the unlocked Exynos versions of the Galaxy S9 and S9+ (starlte and star2lte) will have builds available soon. The Galaxy S8/S8+ never received official support from LineageOS, so the availability of 15.1 builds is a big deal.
Finally, the Nexus 4 (mako) will have 15.1 nighties available soon. That's right - Google's 2012 flagship that came with Android 4.2 can now run Android 8.1 Oreo. That's nothing short of impressive.