Luke kinda talks to Artoo on Yavin before the Death Star attack (when the tech asks if he’d rather use another droid), but it’s a pretty simple exchange (and it kinda feels like Luke doesn’t really understand Artoo’s reply).
That’s the only one I can think of.
The big one I was thinking of was from a deleted scene, wherein Luke is watch the battle over tatooine before running off to tosche station to show his friends. He talks to the droid he’s with, but again, it’s a simple exchange of Luke trying to tell the droid to “Get it in Gear,” before leaving it for scrap. In the radio play it was expanded to a full conversation but still seems to be a little one sided.