I had read about the problems in Russia but figured Sony had addressed this in the revised update. Nope. This is what fixed it for my Xa2:
-Remove the Sim card -hold volume + and power until the phone vibrates 3 times, about 10 seconds. -Then power it up again -the screen is restored you should hopefully be enjoying android pie! -put the Sim card back in and restart again
This worked for me after finding it on a Russian thread.