No icon (lock icon) in panel

Hi everyone,

I was wondering if there is a way to set the icon that should be displayed in the panel (the top vertical bar). Some applications such as Firefox, LIbre Office products are shown correctly (their icon in the panel is the same as the icon in the list of applications).
However some other icons simply show a lock in the panel (while the correct icon is shown in the list of applications). The lock that I’m talking about is the same as the lock before each name of a domain in the list of applications.
The problem happens in fedora-32 and debian-10 based VMs. I tried creating a manual desktop entry in /usr/share/applications and setting the icon to an absolute path there, but that didn’t help either.

So please tell me if you have any ideas how to enforce the icon that is shown in the top panel.

Have an awesome day!

This is a long standing problem (at least 3.0 I think) which should be
resolved in 4.1.
I’m not aware of any genuine solution that works in 4.0 - refreshing the
app-menus may work in some cases - qvm-sync-appmenus.