And thanx to Alldocube for link to wrong instruction – i got a bootlooping brick. I unbricked it from bootloop using the SP MDT Tool and the latest firmware from firmware page and the file auth_sv5.auth (maybe the last file is not needed), and as a result I got a working Android 15 instead of 14.
After updating to Android 15, the size of the icons on the screen does not change after the settings in the menu. The service buttons were initially located correctly, now the triangle and circle are in the left corner, and the square is in the right corner.
