Personally I don't think I'd file a return at all since not required.  Not sure this can be done, considering

now the IRS has a EIN to match to return.  This is why I would file and mark final so to satisify the filing

requirement and close this trust.

Who were the beneficiaries of the trust even though it wasn't funded?  - The T/P's 3 sons.

You could issue zero K-1s to them.  Thought that would be an option and would eliminate the error I mentioned above.

Otherwise I think you'll be stuck paper filing that return.