Bad screen resolution permanently crashes Poco F1
I fixed it* by letting the phone bootloop until fully discharged. I then plugged the phone into the computer and turned the phone on as soon as it charged enough to allow me this. At that point there is a brief window where full ADB access is possible, but only because I did have USB debugging enabled after all, but the bootloop was too fast to allow full ADB access at any point.
I imagine the phone does a fuller/slower reset when discharged. At one point in the &quot;good&quot; bootloop it shows a nice, round, &quot;loading&quot; circle, and that is when I got ADB access. There is little time before &quot;bad&quot; bootloop is resumed.

This is what I kept entering in command line during the &quot;loading&quot; circle boot phase, until it finally indicated that I have the full ADB access by showing the alphanumeric ID of the phone and &quot;device&quot; after it:
adb devices



List of devices attached
    03464364da54  device


Uninstall the culprit app called SecondScreen, by first finding its proper name, and then uninstalling it via adb:
adb shell pm list packages | grep second 

pm uninstall -k --user 0 nameOfTheAppReturnedByTheAboveCommand 


This was not enough, and the phone entered the &quot;bad&quot; bootloop again, so I discharged it again and reset the screen size and density (DPI I believe):
adb shell wm size reset

adb shell wm density reset



It works like new now.