Perfect application for NocoDB in my opinion. They have a relationship view like the one shown in the screenshot and a form builder for easily adding new data. Setting up the relationships is easy. I find it much easier to use than DBeaver and the GUI is more modern.
The data is accessible by programs such as DBeaver, and they have a REST API too, should you need it.
I think it’s cool you’re trying to find ways to get into this. If the goal is to learn, why not deploy the services on your laptop? They won’t be available when the computer is off of course, but you would still get the full experience. Even a low-spec laptop will be better than a cheap VPS.