According to configure.ac it should be still possible to compile pinentry against qt4 however it seems to fail after changes made in 1.1.1:
../.././qt/main.cpp:40:10: fatal error: QWindow: No such file or directory 40 | #include <QWindow>
../.././qt/pinentrydialog.cpp:230:6: error: cannot convert 'PinEntryDialog::PinEntryDialog(QWidget*, const char*, int, bool, bool, const QString&, const QString&, const QString&)::<lambda()>' to 'const char*'
Could you please confirm whether Qt4 is still supported?