The Nexus 5X is the result of the collaboration between Google and LG. It's a solid device that's been recently updated to Android 7.1.1 Nougat, but will probably never get another major OS upgrade since it will be more than two years old when Google releases Android O.
So, instead of throwing the phone into the bin of forgetfulness, the good folks roaming on XDA forums have decided to keep the Nexus 5X alive by any means possible.
XDA Senior Member m4r0v3r managed to cook a port of Jolla's Sailfish OS for the Nexus 5X. It's quite refreshing to know that this type of devices would be able to run just about any operating system out there with a little bit of tinkering.
Since this is the first release, if you own a Nexus 5X and want to check out what Sailfish OS has to offer, then you should know there are still a couple of issues that must be addressed. First of all, there are some functions that will stop working if you install the Sailfish OS port on the Nexus 5X.
For example, if you need your camera to take pictures, you shouldn't install the ROM yet since it will disable the Nexus 5X's camera. Furthermore, the fingerprint sensor and Bluetooth connectivity won't work either.
On the bright side, the creator of the port confirms that the audio (including music) is working smoothly, as well as calls, texts, data and Wi-Fi connectivity.
However, future builds could address these problems, so that Nexus 5X owners can use the Sailfish OS port as their daily driver.
If you're into installing custom ROMs, all the information you need to put Sailfish OS on your Nexus 5X has been posted on the original thread on XDA forum.
Make sure you back up all your information before flashing the Sailfish OS port on your Nexus 5X, since you'll most likely lose everything if you don't.