I have two monitors, one is up to 144 Hz and another is 60 Hz. When I set my primary monitor to 144 Hz, I noticed something weird:
1. I cannot double click the desktop icons to open them unless with an extremely high speed. Just like this thread https://forum.kde.org/viewtopic.php?f=309&t=163827
But I can double click all icons without problems while I set both monitor to 60 Hz then re-login.
2. The Breeze welcome screen spins much more quickly in 144 Hz monitor than the 60 Hz one.
3. The notification disappears very soon under 144 Hz.

OS: Arch Linux x86_64
Kernel: 5.11.6-zen1-1-zen
Resolution: 1920x1080, 1920x1080
DE: Plasma 5.21.3
WM: KWin

Just confirming I have the same problem with a 240Hz monitor, but if I double click really really fast sometimes I can launch from the desktop. Pushing enter on a desktop icon works to launch it.
I'm using Kubuntu 20.04.3.
plasma-desktop = 4:5.18.5-0ubuntu0.1