External opening offers a much better experience than the current silent
ignoring of the user's navigation attempt.

I have tried the following code in place of
QDesktopServices::openUrl(url)):
    auto* const job = new KIO::OpenUrlJob{url};
    job->setUiDelegate(new KIO::JobUiDelegate(
                KJobUiDelegate::AutoHandlingEnabled,
                ICore::self()->uiController()->activeMainWindow()));
    // job->setStartupId(KStartupInfo::startupId());
    job->start();
The KIO::OpenUrlJob() code probably handles errors better, but it is
more verbose and requires including 4 headers. Errors are uncommon in
this case, so I decided to go with the simpler alternative.