While doing this → https://bugzilla.mozilla.org/show_bug.cgi?id=1628002
I’ve noticed today that the .desktop file created yesterday with chromium-as-a-snap appears with its matching icon and is now fully functional, I guess reboot is the key ???
I’d say this one for chromium looks already close enough → https://bugs.chromium.org/p/chromium/issues/detail?id=1066364&q=shortcuts%20for%20web%20page&can=2 ?