Is this prompt for iCloud credentials legit?
Apparently, starting and logging into iTunes and going to the Account -> View my account -> All purchases , as ankii mentioned:


If you don't see your in-app purchases
See your purchase history on your computer


When you go back to Ethernet Status and then click "Restore Purchase" you're already logged in to iTunes and it doesn't prompt for credentials. Problem solved!

Also: Enable 2FA. That's not only a good idea for Apple/iCloud but it always is, everywhere. Whenever 2FA is supported, enable it!. It may be a pain in the behind at times, but the alternative, a hacked account, will be much, much worse.