I'm using KDE dektop and a 'compact' task switcher.

When I'm cycling through the windows to choose which to switch to with Alt+Tab (while holding Alt), all windows apart from the selected one become translucent and the selected window raises to the top. I personally find this very distracting.

Is there any way to turn this off? I want Alt+Tab to only show the task switcher window and do nothing to the application windows until I release Alt to confirm and switch (similar to how it works in gnome3/cinnamon/openbox/many other things).

I experience this with Ubuntu 18.04.5, KWin 5.12.9 and also Debian testing with KWin 5.17.5. However I also recall seeing similar behaviour on older Ubuntu/KDE versions as well.

Go to SystemSettings->Window Management->Task Switcher->Main tab, and uncheck "Show selected window"

Brilliant, that's exactly what I was looking for. Thanks!

Probably this option would benefit from some explanation in the corresponding settings window.