Stylus not working on ELAN2514:00 04F3:29F5 touchscreen (HP Spectre x360 late 2019)

Summary

The HP-provided stylus for the HP Spectre x360 13 aw0053na (late 2019) is not working with the ELAN2514:00 04F3:29F5 touchscreen. Fingers are correctly recognised.

Steps to reproduce

Stylus not detected: no events generated when running libinput debug-events

libinput version you encountered the bug on

$ dpkg -s libinput10
Package: libinput10
Status: install ok installed
Priority: optional
Section: libs
Installed-Size: 344
Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>
Architecture: amd64
Multi-Arch: same
Source: libinput
Version: 1.15.2-1

Hardware information:

HP Spectre x360 13 aw0053na (late 2019); ELAN2514:00 04F3:29F5 touchscreen

Other log output:

$ sudo libinput debug-events --verbose
libinput version: 1.15.2
[...]
event11 - ELAN2514:00 04F3:29F5: is tagged by udev as: Touchscreen
event11 - ELAN2514:00 04F3:29F5: device is a touch device
event12 - ELAN2514:00 04F3:29F5 UNKNOWN: not tagged as supported input device
event12 - not using input device '/dev/input/event12'
event13 - ELAN2514:00 04F3:29F5 UNKNOWN: not tagged as supported input device
event13 - not using input device '/dev/input/event13'
event14 - ELAN2514:00 04F3:29F5: is tagged by udev as: Tablet
event14 - ELAN2514:00 04F3:29F5: tablet 'ELAN2514:00 04F3:29F5' unknown to libwacom
event14 - ELAN2514:00 04F3:29F5: device is a tablet
event14 - touch-arbitration: activated for ELAN2514:00 04F3:29F5<->ELAN2514:00 04F3:29F5
[...]

$ udevadm info /dev/input/event12
P: /devices/pci0000:00/0000:00:15.0/i2c_designware.0/i2c-1/i2c-ELAN2514:00/0018:04F3:29F5.0001/input/input19/event12
N: input/event12
L: 0
S: input/by-path/pci-0000:00:15.0-platform-i2c_designware.0-event
E: DEVPATH=/devices/pci0000:00/0000:00:15.0/i2c_designware.0/i2c-1/i2c-ELAN2514:00/0018:04F3:29F5.0001/input/input19/event12
E: DEVNAME=/dev/input/event12
E: MAJOR=13
E: MINOR=76
E: SUBSYSTEM=input
E: USEC_INITIALIZED=3202764
E: ID_INPUT=1
E: ID_PATH=pci-0000:00:15.0-platform-i2c_designware.0
E: ID_PATH_TAG=pci-0000_00_15_0-platform-i2c_designware_0
E: LIBINPUT_DEVICE_GROUP=18/4f3/29f5:i2c-ELAN2514:00
E: DEVLINKS=/dev/input/by-path/pci-0000:00:15.0-platform-i2c_designware.0-event