Hello,
After the latest Version of Sailfish 3.4.0.24 becomes available yesterday, I decided to flash another device.
Therefore I tried to follow the instructions from the official Sailfish X installation guide here.
Unfortunately it doesn’t work with the Sony sa0114 ADB Interface Driver. Looking on the official Sony website for unlocking the bootloader here it says something about the USB driver.
So maybe it would be good to update the official installation process for windows?
Apparently the Google USB Driver it didn’t work for the two persons that have tried: https://together.jolla.com/question/227831/unable-to-install-fastboot-driver-in-windows-10-v2004/?answer=229288#post-id-229288
But yes the guide needs to be updated, at least to say that it only works on Windows 10 with a version prior to 2004 for now, until there is another reliable solution.
I’ve flashed a device yesterday and found out that we were heard, the doc now contains this exact warning. Thanks to whoever added it 
Of course it would be better if there was a proper solution, had you tried the USB Driver in the end? (I’m still on a 1909 on my side)
I think so, yes. But to be frank I can’t remember it clearly.
The TJC thread above has a workaround using the Zadig software and I can confirm that it works: connect the phone on fastboot mode, let Windows detect it as Android, run Zadig, and then Zadig automatically selects the “Android” device and offers a choice of USB drivers for injection (WinUSB worked fine for me).
Some sailors have reported that letting Windows 10 upgrade to 20H2 also solves the problem.
Yes, updating to the latest Win10 version solves the issue, the guide can be updated again ^^
I can confirm the Win 10 20H2 works for the install. Just flashed my XA2 yesterday.
And for us (stubborn) Linux users, there’s fastboot version issue…