The default Alt-Tab in Gnome 3 switches among applications and windows are grouped by application. How to make Alt-Tab switch among windows instead of applications in Gnome 3?
Check the Alternate Tab Gnome 3 extension and you will love it.
Substitute Alt-Tab with a window based switcher that does not group by application. This extension is part of Classic Mode and is officially supported by GNOME. Please do not report bugs using the form below, use GNOME Bugzilla instead.