Worse: they're reserved with any extension. Have a file in your repository called "aux.rs"? It will cause problems on Windows.
I think you need to be a wee bit pro-active and take a look at your potential deployment targets and try and guard against these types of naming issues. Unix and Linux aren't the only (one true) operating systems in the world.
QString appDataDir = QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);
// ~/Library/Application Support/<APPNAME> on macOS
// C:/Users/<USER>/AppData/Roaming/<APPNAME> on Windows
// ~/.local/share/<APPNAME> on Linux
Also those locations are user specific, there's nothing there to support the use-case of an app that's available to all users, or might just be a system service (/daemon).