Which missions do you have to complete in GTA 5 story mode on PS4 to activate the Duke oDeath?
I'm wrong, but I'm almost certain that it is only available in online mode and not in story mode.
You have to play the prologue, then you can play online and there you can play duke oDeath
There's no story mission for the Duke O'Death. This is a random event that only happens once. In the desert at an abandoned tank opposite (or nearby) the clothing store.