I definitely feel it's better to ask for forgiveness than permission with this sort of thing, council fear of litigation definitely stops a lot of good things from getting off the ground.
Back in lockdown I was part of a little composting/grow your own collective, nothing formal just sharing advice and resources. And we did a little workshop on a local estate to see if anyone wanted a composter or raised beds or anything. And it turned out they didn't but what they did want was a community noticeboard next to the bus stop.