I think I had the same Issue. My way to go was using another device in the end. I wasn’t able to get it unlocked and flashed under Linux on my XPS 13. (This notebook has only USB-C-Ports. I tried different USB-B Hubs and old cables and adapters.) It wasn’t successful for me to try to set the Mode of the USB hub to some other.
Finally the solution was to use another system. Still Linux, but the HW was “older” and had some real USB-B ports.
EDIT: There is some help, which didn’t work for me however: https://jolla.zendesk.com/hc/en-us/articles/115003840273#Trouble
Also I tried some of mentioned USB-Problems here before using another system: Guide: Installing Sailfish X on Xperias - together.jolla.com