Yes I sometimes have a free lunch.
For example; a few weeks ago I dug some new potatoes that had volunteered to grow in my compost pile. (I actually had to turn the pile over, so the digging wasn’t for lunch so no time or effort expense was used for lunch)
I picked some black raspberries that had volunteered to grow behind my garage, (about a cup and a half, I didn’t consider it work, it was pleasurable to be out in the morning air.)
I made a salad out of some greens and had zucchini, that I was given when I dropped off some clothes at the Human service office. (a bit like like goodwill) They had an over abundance given to them by a local gardener, it needed to be used while fresh and they didn’t have enough clients to take it., so they were giving it away to anyone who would take it.
That day I had a free lunch and a free dinner. The only kind of expense to me or anyone would have been the cooking, but; I cooked the potatoes and zucchini in the oven while I was baking a pie for a charity dinner that was the next day. I would have had the oven going for the pie anyway, and didn’t run it any longer while I also cooked the potatoes and zucchini.
I often have free food that volunteers to grow, or I’m given garden plants from friends who have too many. It doesn’t always happen that I have an entirely free lunch, but sometimes it does.