CyanogenMod, despite any goings on with its original creators, is still the bread and butter of the custom ROM world. The newest version, CyanogenMod 14, is based on Android 7.0 (Nougat) and is only now beginning to be built up and fleshed out upstream in CyanogenMod's community repositories. Many of the features that CyanogenMod is famous for, like extended system settings and the well-known Theme Engine are still being worked on, are broken, or simply aren't baked into the ROM's bases yet. This hasn't stopped ROM builders and maintainers from grabbing the latest versions of everything from upstream and compiling the ROMs for a few devices that are particularly easy to build for. The OnePlus 3 is one of the first few devices to find itself with a flashable, booting, usable version of CyanogenMod 14, and it's far from alone.
A quick Google search will turn up unofficial builds for an already decent roster of devices. The Motorola Nexus 6 and LG Nexus 5 are already on board, as are multiple members of LG's G3 and G4 flagship families, a few older Samsung devices like the international Galaxy Note 3 and S4, and even a number of Moto E and Moto G devices. As for OnePlus faithfuls who haven't gotten their hands on the OnePlus 3 just yet, there are builds floating around for the likes of the OnePlus One, OnePlus 2, and the OnePlus X. Even the downright ancient HTC HD2 is getting in on the fun. While many devices are still waiting for any Nougat love at all, the number of devices that are already seeing quick and dirty builds of CyanogenMod 14 is quite encouraging, to those who follow the custom ROM development community.
While users who flash CyanogenMod 14 at this stage shouldn't expect more than a bootable Nougat build, this is CyanogenMod we're talking about, so even without much involvement from the original crew, it's safe to say that this ROM is quite likely to see the quickest community development. Conversely, a good number of bigger ROMs like SlimROM and Dirty Unicorns are just ironing out the kinks for their versions of Android 6.0 Marshmallow, and a number of small-name Nougat ROMs, like Nutty Nexus for the Nexus 6, are popping up on sites like XDA Developers and elsewhere. Anybody wanting to take the plunge is advised to do some reading beforehand, of course - as there are still some caveats with any Nougat ROM or build, let alone an early build of CyanogenMod 14. For example, the OnePlus 3 has a non-functional camera with CyanogenMod 14 at the moment, while the Nexus 6 has a barebones build with barely any features enabled beyond what would be found in stock Nougat. OnePlus 3 owners can head through the source link below for more details on their unofficial version.