This is Qt 6.7.2 backport that runs on Windows 7 (what?). The repository contains patched source files from the qtbase module.
Approach is based on this forum thread but better: many improvements amongst important fallbacks to default Qt 6 behaviour when running on newer Windows.
You can use our prebuild binaries (we used Visual C++ 2019 with OpenSSL 3.0.13 statically linked, see compile_win.pl script) or compile Qt yourself using compiler and build options you need.