When you say "in the city", how much land are you talking about?
I live in a fairly dense city, but my neighborhood is still largely either single-family homes or former single-family homes that have been divided up into small apartments. In other words, there are still yards. I have a moderately large yard for the area, at about 6200 square feet, or a seventh of an acre, minus the area of the house.
My son's family are a little overwhelmed with a yard about twice as big in the suburbs, with chickens and trees and veg and play structures, and pets and too much work to do.
As an elderly woman without much traditional gardening experience, I find this is plenty of land for me to steward. There is light pollution and noise pollution and occasional vandalism and fruit theft, but there's also a lot of satisfaction. I prefer working on things that are in poor condition so I can improve them and not worry about my mistakes messing them up.
This house when we bought it was falling apart: roof, floors, windows, doors, electrical system, plumbing, walls, foundation all needed work. Repairing rather than remodeling or tearing it down conserved hundred-year-old materials and much human investment of effort and thought.
The yard was invasive toxic bulbs and ivy and poke and blackberry and trash and broken glass. Now it's a forager's plot with dozens of fruit trees, mushrooms, vegetables, fiber and medicine plants, as well as places to nap and host dinners. I have conserved and brought in woody debris, so the soil gets better and water sinks in. There is always work to do. It's kind of a bonsai food garden. Good thing I like pruning. The weeding is impossible to keep up with. My "zone 5" is a 5 foot diameter thicket in the back corner.
I have been working on a book about my experience here. If anyone wants to read it and comment I'd be thrilled. It's mostly about particular species in my particular climate. Maybe I should broaden its scope.
I'm happy others are thinking about city permaculture also. I am convinced that unless city people have a lived connection to the earth and the sun and the water, all our efforts to "save" our home planet are nothing but an abstraction, with no real conviction, just ineffectual, out-of-context sentimentality.