This is a great question. I don’t stutter but I am an SLP! I would say to just be honest and upfront about it. Don’t run away or avoid hanging out just because of this one thing. You’ll be so glad that you got it out of the way and regardless of his reaction you’ll feel weight lifted off of yourself. I think how you bring it up kinda depends on what you prefer- in person or before you meet him and that will sort of shape how to word it. Either way talking about it is a great way to break the ice esp if you have anxiety about it. If he’s worth your time, it won’t change anything and he may even find it interesting.