On today's Lucy launch stream a huge torch was visible nearby. First stage was kerosene-powered, second was using hydrogen. I wonder if this torch is to burn hydrogen byproducts?
The torch would, most likely, be for emergency methane venting. They had previously used a torch for burning gaseous methane during de-tanking, but have since switched to a condenser to cool it back to a liquid. There would essentially be no reason not to continue that practice, particularly when they'll have a nearly unlimited supply of liquid nitrogen.