Getting fully official CyanogenMod support, complete with nightlies, is sadly not something that happens to every device out there. For the devices that do get the nightly treatment, it can be seen as a badge of honor or sort of coming of age, except in extremely popular flagships where CyanogenMod support is almost inevitable, if it's possible. While a large number of phones fall by the wayside or have a roadblock like a locked bootloader in the way, a good number of modern devices do end up getting community support beyond their official end of life. Huawei's ultra-budget Honor 5X is the latest lucky device to get official support from the CyanogenMod team. Specifically, the phone has its very own branch of CyanogenMod 13, based on Android 6.0 Marshmallow.
The build of CyanogenMod 13 for the Honor 5X is maintained by crpalmer and BadDaemon, with the official thread on XDA Developers handled by crpalmer. The build is quite fresh, having only been originally posted on August 2nd, and as such, still has a few bugs to work out. While some of these bugs may disappear with time, others may be rooted in bits of code to interface with the hardware that are either oddly implemented or are kept under lock and key by Huawei, meaning they may never get fixed. For the time being, those bugs include a lack of support for HDR photos, no love for flip and smart view cases, and the proximity sensor disabled for the double-tap to wake function, in order to avoid false wakeups.
The ROM is available for download right now on CyanogenMod's official website, and can be used with or without a Google Apps package. Officially, the recommended Google Apps package is OpenGapps, as with most custom ROMs. Going to the thread for support will require a logcat for any bug reports, as is customary, and users who use system modifying apps like Xposed Framework will find no love, since those apps mess around with essential system files and can cause a whirlwind of issues all their own. The ROM is still in early development, but if you're willing to take the plunge and replace EMUI, head through the source link and give it a shot.