Most venues where we camp allow us to have fires, often raised off the ground fires. At these venues, we also protect the ground, usually by placing firemats and/or firebricks on the ground under the fire pits.
At venues that allow us to have a fire in the ground, we usually have to remove the sod intact to have the fire, and then replace the sod once we are done.
Either way, we attempt to respect venues to the best of our abilities.
Fire should not be left unattended!
They should be put out before going to sleep or leaving camp.
Most of the time, modern items can be hidden away in tents. Tents that are used as displays, whether patrons enter them or not, would need to reasonably hide modern items.