When the OnePlus One debuted back in 2014, it was sold as an enthusiast phone with insane bang for the buck. Fast forward four years, and Android 8.1 Oreo in the form of LineageOS 15.1 has just been released for it. The OPPO Find 7a and Find 7s and Galaxy S5 Plus/LTE-A are getting 15.1 as well, and the Huawei Ascend Mate 2 4G has returned with LOS 14.1.
The OnePlus One may no longer be officially supported by OnePlus, but it's now receiving Android 8.1 Oreo via LineageOS 15.1. Its sister phones, the OPPO Find 7a and Find 7s, have had their builds unified, and are also getting LOS 15.1 right now. The Galaxy S5 Plus/LTE-A (an S5 with a Snapdragon 805 and 3GB of RAM) rounds out the list for 15.1 receivers. Lastly, the Huawei Ascend Mate 2 has "returned from the dead" with a LineageOS 14.1 build.
You can download these latest versions via the links above, or if you've already got LineageOS on your phone, you can download through settings.