Charlie Vickers, the actor who played Sauron in The Rings of Power was interviewed in various publications, and suggested that it was made deliberately vague in the TV show if Sauron did actually repent:
NYT: You once mentioned that you found useful things in Tolkien’s letters, although you didn’t specify which ones. I took that as a possible reference to the period in which Sauron sought redemption. But then the showrunners talked recently about another way to read Sauron-as-Halbrand: as a power addict. What was it that you found in Tolkien that helped shape your portrayal?
Vickers: I think the repentant Sauron is a really interesting thing. But I like to leave it ambiguous because it was ambiguous in Tolkien’s writing, such as in Letter 131, and in “Morgoth’s Ring,” in the History of Middle-earth series. He spoke of Sauron repenting “if only out of fear.” I think his repentance is fascinating — and this is why I don’t want to say necessarily how I interpreted it as an actor — because it creates two different [possibilities] for Halbrand.
If you look at him as if he’s genuinely repentant, and he wants to escape this dark path and live as someone who’s been humbled, then Galadriel inadvertently draws him back to this power. She says to him in the smithery, “There’s no peace here,” and that scene illuminates this whole idea for him of: “Well, you’re right, there is no peace for me as a regular person. My peace is in power. I need to rule. I need to lead.” And she literally gives him the keys to the kingdom and sends him back down the rabbit hole. That is, if you view him as repenting genuinely.
But, if you view his repentance as an act, then it leans more into his deception, and his deception of her, in that she’s a tool for him to get back to where he wants to be. You rarely see Halbrand alone before the finale, save for this moment when he’s in the smithery, staring at his pouch, making his decision. Otherwise, you mostly see him through the eyes of other characters.
- ‘The Rings of Power’: Charlie Vickers on That Monster Revelation. The New York Times (emphasis mine)
EW: Throughout the season, we've watched as Halbrand has gone on an almost redemptive journey, and at times, he appears to be seeking peace or even forgiveness. Do you think there's some truth in that, or is that all a smokescreen?
Vickers: I think it's fascinating to look at. It's interesting because Tolkien speaks of Sauron as repentant. He quite clearly says that he is repentant, and he is ashamed. He says it in The Silmarillion, and he says it in some notes in Morgoth's Ring. But he always puts the words "out of fear" right after "repentance." I think fear can lead one to genuine repentance, and I think he fears the gods and he fears retribution. He kneels before Eönwë and is humbled and brought low. So, I think Halbrand is an example of him in this repentant stage.
Whether or not you view that repentance as genuine completely colors his actions of the season. You can look back at his actions, and they can be genuine repentance and it all makes sense. But if you look at him as manipulating everything and using Galadriel to bring him back… Of course, there are some coincidences that happen along the way, which play into his hands. But he is able to manipulate people.
I have a clear answer as to what worked best for me, but I like to leave it kind of ambiguous for the audience because it creates a bit of interesting discussion. It makes it cool to look back on and leave it to interpretation, I think.
- Sauron speaks! That Rings of Power actor opens up about the big finale reveal. Entertainment Weekly (emphasis mine)
Deadline: There are obvious similarities, like Halbrand and Sauron are both skilled smiths. What are some of the more subtle clues about Halbrand’s true identity that you as an actor dropped along the way during the season that we may have missed?
Vickers: [...] I was hoping that this would happen when creating the character that people were going to be like, is he genuinely repentant, is genuinely trying to be a good man and start a new life? Or is he just manipulating his way through it? So when you look at that scene and you think, well, he’s conflicted, he’s just by himself, he’s not showing this to anyone, you could argue that, well, perhaps he is genuinely repentant.
But I remember making that scene and thinking, in Middle Earth, there is always someone watching and the gods are watching and he fears the gods.
So I think for me, as I was performing it, it was about accentuating the subtle differences within that repentance and not being too obvious with either manipulation or overt conflicts. Like, I really want to be a good man. I think I tried to walk the line. And as well as that the showrunners, the writers put in some really cool little hints along the way, lines like to Galadriel, ‘I’m sorry about your brother.’ Or I think his second line on the raft is ‘Looks can be deceiving’. [...]
- Behind ‘Rings Of Power’s Sauron Reveal As Actor Speaks About Secret Identity & Clues Fans May Have Missed. Deadline (emphasis mine)