How to completely disable user interface sound effects?

Even though I've unchecked the "Play user interface sound effects" option in the System Preferences, sound effects are still played, for instance the "Boop" sound when an action isn't available – and this also happens in applications that have no sound effects of their own. Any suggestions how to completely disable all such sound effects?

(I've just moved to a new MacBook Pro; I never had this problem on my old MBP, also running macOS Monterey.)