Hmm, that's a fair point. I guess it's more of a feature request than a bug then, especially if the intended use-case is for docker hub to be used.
I've noticed that, upon reboot, the /etc/docker/daemon.json file I created (via the command line) to allow insecure connections to my private repository disappeared. Seems as though my intended setup, in its current form, is even less compatible with unRaid than I originally surmised. I guess should private repositories become a supported feature, it would be nice if this configuration option (insecure repositories) were made configurable via the WebGUI and stuck after reboots. That's in addition, of course, to updating the implementation of the "update available" indicator to support private repositories. All-in-all, def exceeds the scope of a bug fix.
But anyway, thanks for the insight Squid! In the meantime I think I'll stick with public docker hub repositories. I'm not too worried if the images I'm creating for my NAS are public -- there's nothing sensitive or proprietary in them
Cheers!