If the main server is slow, use official mirrors (China: mirrors.tuna.tsinghua.edu.cn/qt/, Germany: ftp.fau.de/qt/). Always ensure the URL path ends with /5.15.2/ and the filename contains opensource.

sudo apt install build-essential libgl1-mesa-dev libxcb-xinerama0-dev

GitHub-hosted runners do not include Qt 5.15.2 by default. However, you can upload the installer as an artifact or use actions/upload-artifact and download-artifact to cache it across workflows.

  • Accept license (GPL/LGPL for open source).
  • Install (~2–4 GB).
  • Add C:\Qt\5.15.2\mingw81_64\bin to system PATH if using command line.