Had the same issue with Macbook Pro Mid 2012 my machine just didn’t like the update. Trying to go back to El Capitan from Catalina I got the same error message using internet recovery or using a USB install stick “ Can’t download the additional components needed to install Mac OS-X” . Changing the clock time back to an earlier date in terminal as Dan & abraman suggested did the trick. I already erased my HD so needed to launch terminal during recovery/install and make sure you remember to turn off wi-fi if you previously tried recovery from internet. My install only took about 20min once I changed the time.
Great info on this post thanks for the help