I was just handed these coupons during an order at McDonald's. I don't know if this is regional or local or nationwide... they don't say. I picked em up in zip 44130 (cleveland ohio).
It says valid for new customers only but I don't know if that means people who have never used uber eats or have never ordered mcdonald's specifically through uber eats. Sorry for all the missing details gang, but figured I'd share in case someone can find helpful.
Edit: "For anyone trying this one, it seems you can't go to your account and add the promo code; you have to start an order from McDonald's, get to checkout and put the promo code in there. That's what worked for me." -SinisterBlur (thank you!)