Check system settings for a keyboard entry / applet. I’m on LMDE Cinnamon and have no idea what the equivalents are on Kubuntu, but over here it’s definitely possible to change/remove the default keyboard assignments and set up custom ones instead.
For example, I have Shift+WWW (the multimedia key that starts a web browser by default) set to start the browser with an alternate profile. I could just as easily set plain old WWW to, say, start a terminal instead, or run that custom command.
The hardest part is knowing what custom command to run to get the desired effect.
Do you not know why people would want to block lemmy.ml?