I dumped my ex last week, after dating on and off for 2 years. We're still friends, and he keeps trying to date me again, even though I've moved on (and he forgets that I know the reason I dumped him is because he keeps cheating on me with his long-term mistress-turned-girlfriend, and wants me to turn a blind eye while he's an eligible bachelor--in a 2 year relationship--who's a whore).

I'm so apathetic to anything he does and says, at this point. We're still friends, but nothing he does, gets a reaction out of me anymore (which is why he thought his gaslighting would work, but I treat him like a roommate--we flirt, he gets what he needs, and he goes back to his girlfriend).

So, my question is, what are ways to show my ex I'm unbothered when he tries to flirt with me?
Wehn we were together, we'd talk for months and years on end, and he'd only turn his read receipts off when he was with his mistress (and when I found that out, I told him I was dumping him--which immediately made him turn his read receipts on).

His gaslighting & deception no longer work--he's a boring sweet-talker, who comes across as charming, but he's definitely going to create broken homes as an absentee father in the next 5 years. And I'll be happily moved on, and his "One who got away", while not giving a damn about whatever naive new mistress/girlfriend he's got, while claiming he misses me for the 6,000th time to gaslight me. He loves having his cake and eating it too - he's showed me this, time and time again, so I'm fully unbothered when he tries to sneak his way back into dating me.

So, we're just friends, and nothing he says or does affects me. We've both moved on, but I'm nobody's fool--he's always pretending like I don't see through his BS. He wanted to have his cake and eat it too, and I decided to become emotionally invested in someone else, who has never treated me the way my ex did. And with the added benefit of my ex and I being just friends now.