There were notes on how to make a backend, there were notes on how to use a ready-made backend.
But you can do it without a backend at all: the UI connects to the database directly.
To do this, you will need to take care of making application users database users and configure security, but there is nothing supernatural here.
How much is it possible to hack a database server that looks at the Internet and is configured correctly? It’s not clear yet, but it’s hardly easy. Especially if the application is on a corporate network and not on the Internet.
Flutter completely поддерживает direct connection to databases. This means that mobile applications and desktops can use this. And another video: Observable Flutter: Dart + Postgres.
Another video on the topic, but already Java: Direct2DB: Radically simplified app architecture with Kotlin by Mike Hearn. This example is based on [Kotlin Compose](https://www.jetbrains.com/lp/compose-multiplatform /), but you can also use JavaFX (is it still alive?).
I am not sure that I will give up everything and run away to do this, but as an opportunity it is worth considering.