Windows 10 Fastboot Driver My Sony Z3 Compact is currently unusable and I would like to flash the Marshmallow version of FXP.

Unfortunately it seems like I can't find any fastboot (or as device manager calls it: S1Boot Fastboot) driver for Windows 10.

Am I looking somewhere wrong or is there simply no fastboot driver out there for Windows 10 yet?

Regards
By looking at the inf file, you can find that it tells to use the WinUSB driver. So there is a better solution than disabling driver signature enforcement, you can use the tool Zadig (http://zadig.akeo.ie/). This tools create a self-signed inf for this specific device, using ephemeral keys, added to the trusted certificate store (for this only device / inf), removing the need to disable signature check.

So you can do this : 


Download the tool, start it.
Select the "S1Boot fastboot" device
Select the WinUSB Driver
Click Install


And then fastboot devices list your device.