I am using Ubuntu and Gnome. If I want to switch from one app to the other I can use Alt + Tab - perfect! In my current Gnome environment, one app for example Nautilus is able to start more than one instance. Alt + Tab hops over all Nautilus instances at once. What is the shortcut to switch between all 'own' instances of an app in Linux Ubuntu Gnome.
If you Alt+Tab
to nautilus and wait 1sec (or hit down arrow) it will pop up all instances and you can "arrow navigate" them.
OR
Alt+Tab
and when you reach to nautilus hit alt+` (key above tab)