Thanks, JKSH, that worked. (That is, switching, in Creator 7, under Projects --"Build and Run" to "Desktop Qt 6.2.4 MSVC2019 64bit".)

For anyone with the same exact issue, I might as well point out that with the compilers and debuggers on my machine downloaded with my MS Visual Studio 2022, I was able to compile and run (and have the example program detect Bluetooth LE devices).

However, to get debug mode to work, I had to (as per QT Creator documentation) download the MS CDB debugger. Which I did, within the "debugging tools" part of an MS Software Development Kit. (And then point QT Creator to that binary to make if part of the "Desktop Qt 6.2.4 MSVC2019 64bit" toolkit.

And now everything works!

Looks like this is a known issue https://bugreports.qt.io/browse/QTBUG-80770 and https://bugreports.qt.io/browse/QTBUG-78488.

A workaround is to add:

QTimer::singleShot(0, [=]() { service->discoverDetails(); });