I did this and the touchpad started working. Then shortly after stopped again (er, wasn’t really paying attention to what I did, I was concentrating on getting DP ALT over usb-c to work, which it did after reordering some expansion slots.)
Since then I tried:
- Ubuntu 22.04 (worked)
- Xubuntu 24.04 (a second fresh install – busted still, though the installers live cd still worked)
- Ubuntu 24.04 (worked)
When it was broken, there were missing pointer devices under xubuntu as listed by xinput list
When it works there are two “PIXA3854” devices.