Ok, mate, so you can find "Android Phone" in Device Manager, right?I had done this procedure and I get on other devices S1boot Fastboot. I tried to install 5 different downloads with drivers from android, official xperia, etc, but none of it works. Also I followed this CMD procedure https://forum.xda-developers.com/showpost.php?p=74528751&postcount=22 and again nothing. Do you have an idea how to install the drivers on win10 with all the official updates?
I'm on Windows 10 also, and I use "Android Composite ADB Interface" driver by Google that works well.
You can get it from https://dl-ssl.google.com/android/repository/latest_usb_driver_windows.zip?hl=en , I think.
Extract the zip file, go to device manager, select S1boot device -> properties -> Driver -> Update Driver -> Browse my computer... -> Let me pick from list... -> Have Disk... -> Browse... and point the usb_driver/android_winusb.inf file under the folder you extracted the zip.
Press OK and you might see the list of drivers. Then select "Android Composite ADB Interface" (or Android Bootloader Interface ), and Next.
You might see Warning Message, but go ahead with pressing "YES".
If you've ever installed google drivers, then just select S1boot device -> properties -> Driver -> Update Driver -> Browse my computer... -> Let me pick from list... -> Google -> select "Android Composite ADB Interface" (or Android Bootloader Interface ) and so on.
And to verify the installation, go to the folder where fastboot.exe is located, and run the command "fastboot.exe devices", you'll see your device.