Welcome! You will need your usual KX3 USB adapter, and a “USB OTG” adapter for your Nexus 5X. Those can be found on Amazon and are usually quite cheap.
Alternatively, if you own a serial to bluetooth converter, this is another possibility. One caveat is the Adafruit “Bluefruit EZ-Link” which is a bit too smart for its own good and is not compatible with Android.
Last - choice is good - you can also use a Pignology “Piglet” to connect over WiFi. You can check out www.pignology.net for more details there.
Hoping this help!