A temporary solution:
$ sudo modprobe -r xhci_pci
… which results in the kworker process disappearing from top, the fans wind down, and unfortunately the ethernet expansion bay doesn’t work anymore but at least wifi does. Keyboard and touchpad also work. And suspend with deep also work well, just tested it.
I assume other expansion bays will stop working too, but the laptop is at least charging: the USB-c pass-through works.