GNOME Bugzilla – Bug 739578
No fullscreen menu item available anywhere
Last modified: 2016-09-22 22:43:24 UTC
the only way to go fullscreen in epiphany AFAIK is to press F11. It would be nice to have a menu item, and according with HowDoI/GAction, section Action Scope [*], this should go in the application menu. As a reference, this is where fullscreen item is in Gnome Documents [*] https://wiki.gnome.org/HowDoI/GAction
I think you're misreading that section; fullscreen is used as an example of a window-specific action that does not usually belong in the app menu. (In the case of GNOME Documents, there is only one window.) Anyway, fullscreen ought to be in the window (hamburger) menu; I think it's probably just an oversight that it's not currently.