Ссылки на загрузку Qt 5
https://download.qt.io/new_archive/qt/5.5/5.5.1/
https://download.qt.io/new_archive/qt/5.5/5.5.1/qt-opensource-windows-x86-mingw492-5.5.1.exe
https://download.qt.io/new_archive/qt/5.6/5.6.3/
https://download.qt.io/new_archive/qt/5.6/5.6.3/qt-opensource-windows-x86-mingw492-5.6.3.exe
https://download.qt.io/new_archive/qt/5.7/5.7.1/
https://download.qt.io/new_archive/qt/5.7/5.7.1/qt-opensource-windows-x86-mingw530-5.7.1.exe
https://download.qt.io/new_archive/qt/5.8/5.8.0/
https://download.qt.io/new_archive/qt/5.8/5.8.0/qt-opensource-windows-x86-mingw530-5.8.0.exe
https://ftp1.nluug.nl/languages/qt/archive/qt/