Things to note when importing an existing QT project into the project

When importing another qt version from a project developed on another qt version

Here is an example of a project previously developed on qt5.12.2, which is now running on qt6.5.3.
cannot be imported directly into the IDE, otherwise various inexplicable errors will be reported.
First, delete the extension .pro.user file, because this file is related to the previous QT version that generated this file.
will be regenerated later under the current QT version. Press Ctrl + O on QT creator to open the interface for importing files or projects.