In kickoff, and on panel, launcher icons that reside in /usr/share/pixmaps are not shown anymore. Reproducible: Always
Can you upload one of the wrong .desktop files
Created attachment 99665 [details] htop.desktop
Thanks for the update. Do you know which update broke it? Qt, KF5 libraries, or Plasma?
The problem was on my side. I had set QT_QPA_PLATFORMTHEME=qgnomeplatform. Commenting out that line fixed everything.