Qt-opensource-windows-x86-5.15.2.exe

: For Windows, it requires OpenSSL 1.1.1 for network-related functionalities. Alternatives for Open Source Install Qt creator 5.15.2 - Qt Forum

During the setup process, look for the "Qt 5.15.2" checkbox under the "Qt" category. qt-opensource-windows-x86-5.15.2.exe

: Do not install to C:\Program Files (x86) because spaces in paths can break older MinGW makefiles. Stick to C:\Qt\5.15.2 . : For Windows, it requires OpenSSL 1

(document 3 above) + the Release Notes (document 1). These two will solve 90% of practical issues when using that exact installer. : For Windows

Qt 5 to Qt 6 Migration Guide (cross-version, but references 5.15 changes)