On my Asus X554LA the F7 key is turning off the screen brightness.
Recently I updated my system with -Syyu, and now when I'm pressing Fn+F7 Plasma is locking screen.
How to return the old behavior of the hotkey?
KDE 5.54.0 / Plasma 5.14.5

So, I found that an Fn+F7 in hotkeys menu associate as "Screensaver", and it's set in Shortcuts - System Settings - Lock Session - Global Alternate. I removed that and added a custom global shortcut for Fn+F7 with the command "xset s activate". The solution is a kludge, but work.