I've just downloaded your Domain Restriction (thank you for making this available!). Unfortunately, when I uploaded it via my Extension Manager, I got an error that the language file installer was not found, and within the plugin, I am only seeing the language constant strings - not the field labels themselves. I then manually copied your language files into my "en-gb" languages folder but the backend of the site is still not resolving the strings. I've also tried clearing cache, and nothing appears in the "discover" tab of my Extension Manager either.
I'd appreciate your help sorting this out so that I can take advantage of your extension!