Can't load QtBluetooth 5.12.0 under Windows 7 or 10

I migrated some code from Qt 5.6.0 to Qt 5.12.0 both compiled with Visual Studio 2015. It has some code using QtBluetooth for regular (no "low energy") bluetooth. With 5.6.0, this used to work perfectly.

With Qt 5.12.0, my app won't load. It reports missing API-MS-WIN-CORE-WINRT-L1-1-0.DLL and API-MS-WIN-CORE-WINRT-STRING-L1-1-0.DLL. I don't understand why those WinRT files are required. Dependency Walker for QtBluetooth.dll reports those libraries as missing.

I tried both with Qt 5.12.0 compiled my selft and downloaded as part of a QtCreator install. I tried both Windows 7 and 10. Always getting this error and I found no information about where to find those libraries or how to have QtBluetooth not use them.

What should I do to be simply able to run a QtBluetooth based app under Windows?