Feel that Gnome desktop ‘Alt+Tab’ popup is slow? There’s by default 0.15
second popup delay when you pressing Alt+Tab on keyboard.
It’s nothing serious for some people including me. But if you want to remove the delay to speed up task switcher popup, it can be done easily via gnome shell extension.
Open Ubuntu Software, search for remove alt tab popup
and install the extension.
It takes effect immediately after you installed the extension. And as noted it effects all kinds of pop-ups.
To manage the Gnome Shell extension, install and open Gnome Tweaks, then go to Extensions tab.