" Allow me / Let me..(equally used and valid), introduce my old friend Duo."
Let me introduce you my old friend, Duo sound a lot more natural to me. It is, however, rejected. :(
Let me present my old friend Duo.
Allow me to introduce my old friend Duo.
Both should be accepted translations.
I agree that’s what one might say, but I doubt either would be acceptable because both omit any reference to “to you”, which the te requires.