Not sure if the question was asked with sarcasm or not, but, me being me, I actually tested it here as soon as I read it: It's instant. OnMouseDown event, if you will.
I don't even know what a "context menu" is in this context. Are we just talking about a general right-click menu? If so, it's instant in both Windows 11 and KDE6 for me (desktop, toolbars, etc).
Or do we specifically mean a context-filled context menu, such as the ones used in the file managers? If so, Dolphin definitely performs better than Windows Explorer, but that's a pretty useless micro-benchmark. The thumbnail and live preview processes are far more processor intensive/laggy in Dolphin/KDE, does that mean KDE is overall worse? No.
It's funny because it's the latest version of Windows that requires two clicks to get a non-broken context menu. It's either that or registry hacks that Microsoft hasn't disabled yet.
Or do we specifically mean a context-filled context menu, such as the ones used in the file managers? If so, Dolphin definitely performs better than Windows Explorer, but that's a pretty useless micro-benchmark. The thumbnail and live preview processes are far more processor intensive/laggy in Dolphin/KDE, does that mean KDE is overall worse? No.