Under iOS, both simulator and physical device, start typing in a QLineInput.
QCompleter will pop open a list.
When backspace is used, the list is closed even when selections are available
and no longer accepts input.

In the attached example, type OM then backspace. Both OMEGA and OMICRON should be in a list as well as us being able to continue typing, though we can not.

Works under OSX. have not tried Android/Windows