Comment 17 for bug 1803600

P52:
"cat /sys/bus/serio/devices/serio1/firmware_id":
PNP: LEN2132 PNP0f13

Confirming a fresh install of ubuntu 18.10 works yields a fully functional touchpad but updating (tested with current kernel 4.18.0-12-generic) renders the touchpad unusable.
Issuing "sudo sh -c 'echo -n "elantech"> /sys/bus/serio/devices/serio1/protocol'" restores the trackpads functionality for the current session as already described.

"dmesg | grep -i elan" yields:
[ 3.167455] psmouse serio1: elantech: assuming hardware version 4 (with firmware version 0x5f2001)
[ 3.179490] psmouse serio1: elantech: Synaptics capabilities query result 0x90, 0x18, 0x0e.
[ 3.191246] psmouse serio1: elantech: Elan sample query result 00, 28, 96
[ 3.202881] psmouse serio1: elantech: Trying to set up SMBus access
[ 4.032146] elan_i2c 0-0015: 0-0015 supply vcc not found, using dummy regulator
[ 4.048144] elan_i2c 0-0015: failed to get resolution: -5
[ 4.048168] elan_i2c: probe of 0-0015 failed with error -5

after echoing "elantech", dmesg shows
[ 2185.669979] input: ETPS/2 Elantech TrackPoint as /devices/platform/i8042/serio1/input/input17
[ 2185.683258] input: ETPS/2 Elantech Touchpad as /devices/platform/i8042/serio1/input/input16
instead of the former last three lines.