When loading a new world in 1.17.10 with the experimental Caves & Cliffs feature turned on, all cave openings ceast to exist and where they would appear are all underwater and shallow. Platforms tested on: Xbox One, Android, Iphone. For now I pretty much have to look in underwater caves beneath lakes to find ores. I have also tested about 12 seeds and still no luck so I will be reporting this as a bug.