For input to work on Nexus 5 (hammerhead), a udev rule has to be added using the following instructions:

Make the rootfs rw using the Ubuntu Touch Tweak Tool (UTTT) Run this command on the device/over SSH: echo 'ACTION=="add", KERNEL=="uinput", OWNER="system", GROUP="bluetooth", MODE="0660"' | sudo tee /lib/udev/rules.d/70-android_additional.rules Reboot device

This fix has to be applied only once. It will become redundant after OTA-17 is released, as there is an open PR to fix it (https://github.com/ubports/android_device_lge_hammerhead/pull/30).