I have installed several icon sets, e.g. faenza via the equinox PPA.
However, they do not appear in GNOME Tweaks > Appearance > Icons.
I have done both ALT-F2 + R and reboot, still not showing.
I cannot activate/use them. There is not really much that can be done wrong when installing them via PPA. So what am I missing?
It was a problem related to permissions.
This output shows the folders exist but as you can see they are not accessible by users other than root.
Change the rights of the folders by executing the command
sudo chmod 755 -R /usr/share/icons/Faenza
and restart GNOME shell using Alt+F2 and then typer
and press Enter. faenza now shows in icon themes.