It is likely not connected via USB, although a lot of the periperals of the Framework are. The Framework I’m using, and the generation before that we’re using as demonstrator at Genode Labs, both have a touchpad integrated that are connected via I2C and some GPIO like pin setup, like other modern x86-laptops we support. For those, we use the touchpad driver you’ve tried too.
Nonetheless, I’m not surprised that the driver does not work for you out-of-the-box. The touchpad driver today is not prepared well enough to automatically just fit. It depends on some pin-controller and pin-configuration knowledge that are nowadays either hardcoded (I/O resources of pin-controller are part of information delegated to platform driver via pci_decode) for few devices, and partly defined via the driver’s configuration (look at the touchpad launcher). Those missing information are part of ACPI discovery that we do not have covered completely at boot time yet. It is possible to gain this information, e.g. by investigating a running Linux system, but it is not trivial, and honestly I cannot provide a howto - maybe someone else can jump in?!
Anyway, it was planned already for last year - but the necessity increases - so we are concretely plan to improve ACPI discovery at boot time soon, and then to automatically determine what is needed, to ease the usage of the touchpad driver for everyone.