[sirsinsalot]

The system predates the popularity of installable PWAs. It is basically an exec spawning a Qt Web view and a server process then the Web view connects to local host. Server process shuts down when the Qt UI is closed. The server process is just Java with a webserver lib.

The binary is built for those OS and installed via installers idiomatic for those systems.

It defaults to use a local sqlite backend but could use any rdbms. Simple really.