How to open GKrellM on all virtual desktops?

[Jerome <jerome@xxxxxxxxxx>]

OK, how do I open an app (GKrellm) on multiple desktops?

I used to used kstart --alldesktops and that worked great, until I upgraded 
KDE and it didn't - seems kstart5 was its replacement. Which didn't work, 
telling me "invalid application" or somesuch. So I switched to defining Window 
Rules. Which worked, until I upgrade to Fedora 34 this morning, and that 
stopped working.

So what's the magic incantation to get 4 GKrellM panels opening on all of my 3 
virtual desktops?