My OWC slot loader ejects discs when I select them in Finder and hit command-E.
My 2016 MBP hasn't even got an "Eject" key.
As long as the item to be ejected is selected (highlighted), keyboard ⌘-E will get the job done, as will the equivalent File menu item.
One could also assign that function to one of the F-keys which isn't otherwise dedicated.
At least on my iMac's extended keyboard there is a CD/DVD eject key which has the logo â imprinted on it (to the right of the F12 key).
