Open-air dining with six feet of separation is almost certainly safe. There's literally no evidence to the contrary despite multiple court orders to produce any.
It's below freezing here right now, currently snowing, and with high winds. No one's eating outdoors. I did it a bit before winter started but this entire season has been a wash.
Unfortunately when restaurants around here could open, they didn't have the required distancing between tables because that'd mean they'd make half the money. Your country culture may vary.