When using the krunner for the first time in a session, it only accepts one character. Typing more characters leaves us with only the last one being significant. After something is chosen from krunner output (after only one char...) all next runs perform well - user can type as many characters as needed.
Created attachment 103285 [details] attachment-32747-0.html
This does not happen when scaling is OFF (in Wayland session, used to be 2x on HiDPI screen). But according to Martin Gräßlin, scaling is not supported as of yet.
*** This bug has been marked as a duplicate of bug 416145 ***