6.x kernels support it, just have to do a couple tweaks.
Install game-devices-udev.
lsof /dev/input/event* will show you all the devices the compositor has open. One of those will be the touchpad acting as mouse. Try the very last device first in what follows - was /dev/input/event22 this time.
udevadm info --attribute-walk --name=/dev/input/event22 - check ATTRS{name} until you find the touchpad device.
Create /etc/udev/rules.d/72-ds5edge.rules but using the ATTRS{name} you discovered above instead of the value below.
# Disable DualSense touchpad acting as mouse
# USB
ATTRS{name}=="Sony Interactive Entertainment DualSense Edge Wireless Controller Touchpad", ENV{LIBINPUT_IGNORE_DEVICE}="1"
# Bluetooth
ATTRS{name}=="DualSense Edge Wireless Controller Touchpad", ENV{LIBINPUT_IGNORE_DEVICE}="1"
See Disable touchpad acting as mouse for more.