Ok, QMK firmware now at: GitHub - cscott/qmk_firmware at x1_carbon_gen10
Everything is working except for the “microphone mute” button (and its LED indicator) (which seems to be nonstandard?) and I don’t really know what to map the thinkpad alternate keys for F9/F10/F11/F12 to, which on this keyboard are “chat bubble”, “telephone handset”, “hang up”, and “star”. There’s probably some media keys these map to on a “real” thinkpad.
The trackpoint works but it needs some tuning for “feel”. As @Karoly_Negyesi pointed out above this is most likely because the qmk ps2mouse driver is missing some of the trackpoint-specific bits present in the linux driver. They can be added; just a “simple matter of programming”.