Many festivals in Australia attract a group of people that are quite proud of being a bit different to the mainstream and would consider themselves as part of an alternative movement. Nevertheless most of them go via supermarkets before an event and stack up on processed packaged food items that last til the last day of the event and beyond.
To me there is no alternate culture; at least not one that will have less destructive impact on the environment, without changing what we eat and how we grow it.
Confest is a great exaple for preparing food on site which allows its participants to get fresh local produce and prepare it onsite. Confest has so called 'cooking circles' or food preparation space that are open for anyone to bring their own food and prepare it potentially together with others that are hungry at the time.
Alternatively this could be organised through the event as part of the ticket price. This way food could be sourced and stored in bulk and prepared by volunteers like an extension of a typical crew kitchen.
If this is a step too far or seems to hard to organise, the answer could be somewhere inbetween. Fresh produce can be sourced in bulk and then split so every participant gets their box of fresh produce and potentially also dry goods that can form wholesome meals when combined.
Get on board yourself, take fresh produce to events anyhow. What could possibly be a better snack throughout the day than fresh fruit?