I have a dual-SIM version of Sony Xperia XZ Premium (G8142) running Android 9. In my "Dual SIM" settings I have explicitly asked the phone to use one of the two SIM cards for "Cellular Data", "Calls" and "SMS messages"
However, every time I reboot this phone, Android suddenly starts popping up a white box in the center of the launcher screen, listing both of my SIMs and asking me to select a SIM card for SMS.
Regardless of what I select, the box disappears for a few minutes, but then pops up again. And again... This happens a couple of times after each reboot, until eventually it stops. From that moment on everything behaves normally.
I would like to determine what is triggering this. I suspect that this is some background app installed on my phone that causes this to happen for some [indirect] reason after each reboot. Is there any Android software tool that would tell me what app (if any) is responsible for popping up such dialog boxes on the screen? The issue is 100% reproducible, meaning I'll have no trouble causing this box to appear.