Qt6 Offline Installer -
The offline installer may include Qt binaries but not the compiler (e.g., MSVC not bundled). Fix: Pre-install MinGW or Visual Studio Build Tools separately. Or use an offline installer that includes the compiler (rare).
There is a significant hurdle for open-source developers regarding Qt6 offline installers. Qt6 Offline Installer
For LTS releases (Long Term Support), offline installers will likely continue to exist. For non-LTS (like 6.7, 6.9), they may be absent. The offline installer may include Qt binaries but
"You're welcome. Remember: a tool that requires permission to run is not a tool. It's a leash. Cut it. Build offline. Stay free." Qt6 Offline Installer