For many 'forgotten' Android devices, a custom ROM is the only way to get a taste of the new newer Android flavors. Of course, other contemporary devices could also greatly benefit from a third-party firmware as it usually gives a tad more control over what's going under the hood at the expense of losing stock software features. Speaking of custom ROMs, probably no other name rings as loud as CyanogenMod's.
based on Android 7.1 Nougat and got just launched for a surplus of diverse Android devices. These are the Google Nexus 5, the Moto X Pure Edition (2015), the Nextbit Robin, the LG G Pad 7.0 LTE, the Oppo R5 and the larger R7 Plus. CyanogenMod is also available for a surplus of other devices, like the LG G4, the Nexus 6P, the original Moto G, and some other exotic offerings.CyanogenMod's latest installment, version 14.1, is
Still, if you're willing to bite the bullet and give CyanogenMod 14.1 a try, follow the source link and look for your device in the sidebar - if you're lucky, you will be able to download a CM14.1 build for it and give it a try.