I have figured out a working udev rule that works for the trackpad/touchpad of the Framework Laptop 16, just in case anyone is still looking:
ACTION=="add", SUBSYSTEM=="i2c", DRIVER=="i2c_hid_acpi", ATTR{name}=="PIXA3854:00", ATTR{power/wakeup}="disabled"
(see my NixOS config)
I was able to figure it out after finding this script by Framework: linux-docs/disable-accidental-wakeup/wakeup.sh at 5f840849623f019b433e5c9d9e8a7d4c55add809 · FrameworkComputer/linux-docs · GitHub
From which I could see that the trackpad device is at /sys/devices/platform/AMDI0010:03/i2c-1/i2c-PIXA3854:00. I got the device udev attributes for rule with $ udevadm info -q name -a /sys/devices/platform/AMDI0010:03/i2c-1/i2c-PIXA3854:00 and wrote the rule using those.