[rebugger]

I can recommend Vaadin[1]. It feels like a successor to GWT, feels natural for backend develops and looks similar to Swing. A big component library is included and it offers binding for Typscript webcomponents (there's a frontend-centric variant of the framework named Hilla too).

Frontend states are held in a backend session, so it's safe for manipulations but i'd only recommend it for management UIs.

[1] https://vaadin.com/

[Rebelgecko]

I've used Vaadin for a small Kotlin utility and really liked it. The learning curve was pretty friendly and there's good documentation on their site.

[BossingAround]

Isn't Vaadin paid? The last time I took a look, I got denied because of licensing.