I can't get this working. Of course I'm not experienced with stuff like this. The phone came with Android 7.0.

In Windows I installed the Flash Tool (Emma), which did not connect automatically. On the Sony pages I found the X was not mentioned with a key to connect to Emma!? (https://developer.sonymobile.com/ope...ported_phones/)
(Edit: After connecting holding the volume up key some extra drivers were installed. Then Emma did connect when plugging the USB in while holding the volume down key. Need to unlock first.)

Then I found that the bootloader needs to be unlocked first. (OK, why not, never mind backing up the TA partition an DRM keys now.)

I decided to get my unlock key anyway. The description says to install the Android SDK, but only the command tools at the bottom. Fine, but this is only a zip file. The Extras folder where I should update a driver is not there, it's probably necessary to install the entire SDK...

I rest my case for now, I'll just wait for a more convenient tool from SailfishOS...