Go to System Preferences > Keyboard > Shortcuts and select “Launchpad & Dock”. Click once on “Show Launchpad” and press Enter. Press the fn key and F3 ...
You can open Launchpad by clicking its Dock icon (it's the very next one after the Finder icon), or by using a four-finger pinching gesture on your trackpad.
You don't have this default setting? Settings > Keyboard > Keyboard Shortcuts > Launchpad and Dock > tick Show Launchpad, set it to whatever you ...
I set a Show Launchpad shortcut (Settings > Keyboard > Keyboard shortcuts > Launchpad & Dock) as Control + Down. It worked for the first day.