Qt Maintenance Tool will install incompatible versions, on older (no-longer-supported) macOS 10.15

At some point relatively recently, Qt dropped support for macOS versions below macOS 11 from their binary builds. This is understandable, as Apple has long since ended support for macOS 10.15 and earlier, so these versions are decidedly out-of-date.

However, versions of the Qt Maintenance Tool that are compatible with those older OS releases, and are able to be run on them, apparently have no protection against upgrading (previously-working) Qt components to newer versions that don't support the current OS.

Recently, on a macOS 10.15.7 system that is unfortunately not able to be upgraded, I launched Qt Maintenance Tool version 4.6.0 (I believe), had it run an update check, and accepted the suggestion to upgrade several components. These included the Maintenance Tool itself (to version 4.7.0, I believe), and Qt Creator to version 13.0.0.

After upgrade, both tools were no longer functional on the system, displaying a dialog box similar to this whenever they were launched:

(That dialog box is from the latest Online Installer download, which is also incompatible with macOS 10.15. The difference being, that tool I downloaded from the Qt website, it isn't something that was previously working on my system, and suddenly "broke itself".)

There should be OS version checks in the Maintenance Tool, to prevent it offering packages for installation that are incompatible with the OS it's running on.