I'm not sure why U2F would be "disabled for security". I guess it's just that nobody has implemented all the required things. For the USB tokens, you need userspace USB HID access and hotplug notifications. I did that in Firefox for FreeBSD :)
https://cvsweb.openbsd.org/cgi-bin/cvsweb/www/index.html?rev...
"remove freenode channel from index, it lacks any form of sensible moderation."
You only have access to the devices which you have permission to access. On FreeBSD, we have a devd config that sets the u2f group on U2F tokens.