Keyboard and trackpad on MBP stopped working

[mkborregaard]

I've got a macbook pro retina early 2015, and recently the keyboard and trackpad stopped working. I'm certain it's a software issue, as booting the MBP with a live Ubuntu USB the keyboard and trackpad work fine.
There is no issue with using external keyboard or mouse. Here's what I've tried:

1. PRAM reset and SMC reset
2. Opened the macbook and changed the trackpad cable to a new one (before I realized it was software-related). Also inspected battery and contacts.
   
3. Boot Mac in single-user-mode - this fails with consistent error message `AppleHSSPIController::_enumerateDevice Start failed`
   
4. Reinstall MacOS from recovery console

None of these approaches helped, and I'm out of ideas. This seems to be a consistently recurring software issue for this model, based on the many many threads I've read about it, but not a single one has come with a solution. MUCH appreciated with help.