For non-web, give the Red programming language a try. Java is also another good one. I am afraid there just isn't a good, robust, free and open source system wh

For non-web, give the Red programming language a try. Java is also another good one. I am afraid there just isn't a good, robust, free and open source system when it comes to client-server stuff. Rapid development tools also tend to be less mature on Linux, compared to OS X and Windows (Mac and Windows have a rich tradition of business/enterprise rapid prototyping e.g. FileMaker, HyperCard, Visual FoxPro). If you are on the Microsoft stack (and don't need gimmicks like multiple screen size support, Material-style shadows and animations), the standard WinForms system is also quite productive. I heard that the new SwiftUI system is starting to bring back the spirit of rapid development too though I have no tried it myself. These days "no-code" systems are also making a comeback with half a dozen new SaaSes showing up on HN every other week.