Vaadin
The Vaadin Framework is a leading product for building web apps using only Java on the server-side while being automagically rendered in the client's web browser using web standards. So while HTTP, HTML, CSS, DOM, JavaScript, AJAX, WebSocket, Servlet, and such are being used on your behalf, you need not learn any of them, you need know only Java.
For no cost, layout your forms procedurally, "add label", "add button", "add field", and so on. This is my favored approach.
Or use their commercial tool Vaadin Designer for a drag-and-drop visual environment to layout the forms.
As for adding and editing records, Vaadin has a data model that makes it easy to bind data to lists, data grid, and detail form. Well documented in a guide. Also video demos on YouTube.
Regarding deployment, you can run Vaadin on top of most any Java Servlet container such as Tomcat or Jetty. By default a Vaadin project has an embedded version of Jetty to run your web app conveniently during development, or you can hook your IDE up to an external container of your choice.
Vaadin in open-source under the Apache licence. Runs on top of Java as do the IDEs (IntelliJ, NetBeans, Eclipse), so you can develop on Linux as well as deploy there.
Whoops, I wrote the below before I noticed your Linux and free-of-cost opensource requirements. They are fairly low cost so I'll leave this section.
Xojo
Xojo is a proprietary tool and language that offers a server-side app execution environment like Vaadin. Easy enough for beginning programmers yet powerful enough for professional developers.
FileMaker
FileMaker is a venerable tool for macOS and Windows to create layouts for exiting records in a simple database, mainly for single table (one list of records).
Works either as a server over network/internet or as a standalone single-computer app.
4D
4D is another cross-platform tool similar to FileMaker but providing a much more powerful relational database engine and server.
Includes a visual layout editor that is highly integrated with the database; it "knows" about the fields in the database record (row).
Works either as a server over network/internet or as a standalone single-computer app.