Application icons in Gnome

Up to F39 it used to work as expected: non-Fedora applications that have their own application icons showed up in the dock with their correct icons. Examples:

  • blender (build from git sources)
  • my own Java applications that I build for work
    (set icons via the usual method java.awt.Window.setIconImages() )

Now these apps show with a generic blue “binary” icon with cogs. Is there something I should do, e.g. rebuild an icon cache? I did try gtk-update-icon-cache but to no avail.

desktop-file-install \
    --dir=${HOME}/.local/share/applications \
    --set-key=StartupWMClass \
    --set-value=WM_CLASS \

What does the StartupWMClass field of a .desktop file represent? - Ask Ubuntu