The icon for Krita has disappeared. The entry in /var/lib/snapd/desktop/applications/krita_krita.desktop is:
Icon=krita
As a temporary workaround, I switched this to:
Icon=/snap/krita/current/usr/share/icons/hicolor/256x256/apps/krita.png
Which works - but it doesn’t feel all that satisfying to have to manually set this, and if I remove the snap and install it again, the setting is lost (I wonder if it will be lost on refresh, too).