I just completed a run with the abandoned deck at white stake difficulty where I went out of my way to avoid playing any flushes with the intention of unlocking this joker.
I checked a couple of times while choosing which planet cards to pick and all throughout the run the “flush” hand type stayed at 0 uses.
Upon losing the run on ante 11 I did not unlock this joker. I don’t know if there is some other criteria I needed to meet, but with the current wording on the card, “Win a run without playing a Flush” I should have unlocked it.
Also if it’s necessary info:
Nintendo switch
1.0.0m-FULL
Also Localthunk if you read this, thank you so much!! You really hit it out of the park with this one 🙌. 11/10 GOTY