Reproducer attached. By default, it is a QLineEdit being positioned at the bottom of window. One can also replace it with QTextEdit, etc., and the issues are the same. One can built it with 6.5.6 and 6.7.2 to see the problem.

Good behavior (6.5.6):
1. Upon clicking QLineEdit so that it is focused, only digit keyboard pops up. Because "Qt::ImhDigitsOnly" says so.
2. The entire window is shifted upward a little bit (I can tell by putting a QLabel on top edge of window), so that QLineEdit is not covered.

Bad behavior (6.7.2):
1. Upon clicking QLineEdit, it is still full keyboard.
2. No shift happens and QLineEdit is completed covered. One can't see what's being input.

Update: not a QWidget issue but a more generic input method/platform integration issue on Android. QML text input components are also affected. A separate bug report for QML issue is created:
https://bugreports.qt.io/browse/QTBUG-128378