Some dance events don’t allow photos or videos, or they have a videographer/photographer, but not when you want, and not giving you access to the full recordings.
Want to learn by watching yourself? Want to send videos of yourself to a teacher / friends / family? Want videos for an audition / promo reel / social media post / music video ?
Feel free to video/photo your dancing. If other people are in the frame, don’t post anything publicly without their permission. Best to stick to one end/side of the room to not get too many other people in frame – let’s say cameras are allowed in the back third of the room.