Rules are an awkward, hamfisted attempt to spell out the norms, so take them as subordinate to the culture, and not ends themselves. In other words, if you are killing the vibe, it doesn't matter how much of a smartass you are with rules lawyering.
That being said, you can find some general guidelines on expected behaviour at KWR below:
1. Don't be a jerk.
1a. Don't set out to intentionally insult or offend someone. Be excellent to each other. If you can’t manage that, at least be civil. Avoid insults and personal attacks, do your best to de-escalate conflicts, and consider the effect your words will have on others. Friendly banter and ribbing is just fine, so long as everyone’s enjoying themselves.
1b. Don't make sweeping, negative generalizations. Don’t make broad negative generalizations or disparaging comments about people on the basis of their identity, life circumstances, et cetera. A few examples: people of color, men, high school dropouts, trans people, white people, autistic people.
2. Be Intellectually Honest. During discussion, use a framework of "what can I learn from the other person?", rather than "how can I win this argument?". Engage in nuance, and whenever possible, steelman the other person's point. If you're interested in reading more on this, check out the Basics of Rationalist Discourse. (Despite the title, this is some pretty advanced stuff. Consider the conventions in the link to be what a level 10 rationalist does, while the group operates at level 3.)
3. Assume good faith. Some of us are awkward nerds with middling-to-bad social skills, and since might be talking about controversial things, it's possible that at some point your sensibilities are going to be offended. When that happens, please interpret the other person's point in the most charitable light. (If someone genuinely seems like they're setting out to annoy you or worse, talk to the organizer about this.)
4. No math or coding talk!!! Some of us in the meetup are not in STEM and can't follow the conversation, and some of us are people in STEM who are not interested in talking about it in their off hours. I have a rolled up newspaper that I will use to bonk you on the head if you start talking about math or computer science too much.