piranha VS FlatLaf

You can still mix and match APIs at will with EE. This is what you do on Tomcat mostly, but also with Piranha Cloud (https://piranha.cloud), and to a degree even with Open Liberty.

Not necessarily. Piranha Cloud is an implementation of the Servlet API that is not a container.

Piranha Cloud uses the Java Module system extensively. See https://piranha.cloud

JVM UI isn't so bad. I've written some pretty modern looking UI with it. The sophisticated controls are all there.

Modern JavaFX theme: https://github.com/mkpaz/atlantafx

Modern Swing theme: https://github.com/JFormDesigner/FlatLaf

And these days Compose Multiplatform: https://www.jetbrains.com/lp/compose-multiplatform/

I tend to use Kotlin rather than Java but of course Java is perfectly fine too. You can also use Clojure.

If you use any of those frameworks you can distribute to Win/Mac/Linux in one command with Conveyor. It's free for open source apps and can do self-signing for Windows if you don't want to pay for the certificates or the Store (but the Store is super cheap these days, $19 one off payment for an individual). Also supports Electron and Flutter if you want to use those.

From those frameworks you can then access whatever parts of the Windows API you want. Flutter even has WinRT bindings these days! So it's not quite so bad.

FlatLaf, a modern open-source cross-platform Look and Feel for Java Swing desktop applications, brings exciting new features in versions 3.0 and 3.1 🎉 😀

Here’s the link to the “extras” subproject, and there you’ll find a section on the “UI Inspector” tool.

Swing with FlatLaf - https://github.com/JFormDesigner/FlatLaf

Take a look at FlatLAF:

https://github.com/JFormDesigner/FlatLaf

They have done a great job bringing a modern appearance to the Swing components.

Creating your own Look and Feel is a huge task (just look at the size of e.g. the FlatLaf code.

I too find it a bit frustrating at HiDPI. Best I've come up with is to use https://github.com/JFormDesigner/FlatLaf

And as far as Swing's aesthetics, I only agree with the sentiment that 'it's ugly' if a custom LAF isn't used, like one from flatlaf.