Attached test app has a boolean property isInputMethodVisible bound to Qt.inputMethod.visible.

When running the test app on iOS26 beta, it turns true if you just deploy the test app in portrait and then turn it to landscape (without touching TextField).

isInputMethodVisible: true
Tracking element window has a non-placeholder input view: (null)
Tracking element window has a non-placeholder input view: (null)
Tracking element window has a non-placeholder input view: (null)
Tracking element window has a non-placeholder input view: (null)
Tracking element window has a non-placeholder input view: (null) 

When running the test app on iOS18.5, isInputMethodVisible behaves correctly, i.e. turns to true only if you tap TextField which opens the keyboard.