So I've been observing some obnoxious behavior on my Fedora laptop for a while. If it thinks it can't get through to the network, it concludes you're behind some sort of captive portal and throws up a full-screen browser window to facilitate your negotiations with the local network overlord. I find this annoying; I never do anything full-screen and certainly don't appreciate full-screen windows appearing out of nowhere while I'm trying to get something else done. It's not quite the distraction-free experience I was hoping for.
A recent discussion (http://permalink.gmane.org/gmane.linux.redhat.fedora.devel/206324
) on the fedora-devel list made it clear that I wasn't the only one who feels this way; extra hilarity ensued when Fedora's infrastructure had trouble and everybody
started getting these delightful screens, regardless of the actual state of their network connection.
It turns out that this is a NetworkManager feature at the lowest level. Dan Williams explains it in "NetworkManager for Administrators part 1" (https://blogs.gnome.org/dcbw/category/networkmanager/
). Therein he says that, if one doesn't want this behavior, all that's needed is to remove the NetworkManager-config-connectivity-fedora package. Good enough, I can handle that.
...except that the Fedora folks, in their wisdom, set up that package as a hard dependency for gnome-shell, making it essentially unremovable. So one must resort to editing a config file in /etc/NetworkManager/conf.d (or supplementing it with a higher-numbered version - the recommended approach) instead. That is now done here; I'm looking forward to swearing at my computer just a bit less in the future.
(FWIW, I've been messing with Arch Linux on another machine - article coming soon. It has its annoyances as well, of course, but they seem to do pretty well at avoiding this kind of pain).