If for some reason the app icons do not show up in gnome-software, it may be due to flatpak, and especially that flathub needs to be set up as a distant repo for flatpak.

So you would need :

sudo apt install flatpak gnome-software-plugin-flatpak

And then :

flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo

At the end, kill gnome-software and delete the cached data with :

killall gnome-software
rm -r ~/.cache/gnome-software/