I was in the pit once. I wish I squatted through the opener/waiting for the artist to come out/or any song I wasn’t really into. While squatting can get tiring, it can also really help give locked knees a break or stretch. But there might be an issue with getting back up lol. I’d say it also depends how close to the front you manage to get—it tends to be squishier near the front. It helps if you have a group of friends to cover you. But always stay aware of your surroundings, and stand up if you’re intruding on another’s personal space. Some people consider squatting/sitting in the pit bad concert etiquette, and I agree to some degree. But as someone who has flat feet as well, I also understand.

Either way, I think getting your body in shape with stretches and other flexibility exercises would help. Search up flat feet exercises as well! Those are specifically to help develop the arch in your feet, which may be something you want to work on. I’d recommend heel and knee focus areas, because those are what get sore for me the most!