EDIT 2: "Ignore built-in trackpad when mouse or wireless trackpoint is present" box disappears only if one use Airport.app (that simulates an ethernet BT to surrogate WIF). Using your EFI without any modificatione and without Eliport.app, the box is present..
anyhow, with you EFI on the second ssd, the trackpad starts only at first boot, but at second boot disappeared without any intellegible reason (indeed, ioreg said that trackpad is ok). I tried to move you efi folder several times on EFI partition and doing the VRAM-reset: the trackpad works sometimes, but only until the first boot..
I don't think I have any other choice: I have to use Wifi (so have Airport), and use an external mouse, because other systems and other airport kexts don't work. At least until I understand what the interference is blocking the built-in trackpad..maybe, I'm too old (56 years old) to really understand hack. I already have one fully functional (on a Chuwi Corebook Pro i3), I have to settle for this other one on Lenovo with some limitations (essentially trackpad and WiFi that are mutually exclusive).
Thanks for all your help and forgive me for boring you ..
I will try to understand better, even if I doubt I know how to do it!