[zerr]

Gtk is hardware (GPU) accelerated, while Qt Widgets is software/CPU-rendered.

[DiabloD3]

I notice you say, specifically, Qt Widgets.

Yes, classic Qt Widgets still doesn't allow for hardware acceleration.

However, the majority of Qt UIs you deal with are in Qt Quick, which is hardware accelerated. Almost all of KDE is Qt Quick, for example.

[zerr]

Yes, I was considering C++ (and C) desktop UI toolkits. Unlike Qt Widgets, QML/JavaScript is a horrible mess and not suitable for desktop software.

[DiabloD3]

When I'm on Linux, I use KDE exclusively now (although I'm hoping Cosmic replaces it someday). The apps that use QML are fine even on decade old CPUs with absolute shit iGPUs, still better than even absolutely awfully designed WinUI apps.