I've tried a few of them on iOS and they have all worked well. Some work over wifi and some over a connected USB cable. I tested these:
http://iriun.com (open source, free, works over wifi)
https://reincubate.com/camo/ (free, upgrade for more features, works over cable)
https://neural.cam/live/ (free, upgrade for more features, works over cable)
mackatsol|4 years ago
crummy|4 years ago