How to make images with background-attachment: fixed display properly on iOS?

Question

css

Hello!
The site implemented the effect of changing images through background-attachment: fixed. An example at the link https://codepen.io/orangerise/pen/dyYJYzj
They are not displayed on iOS.
I read that the icons will be visible if you put background-size: cover; but in this case, the images are stretched and only the magnified part of the image is visible on the iPhone.
Can you tell me how to implement this effect for iOS? Maybe there are alternative options for such a change of pictures on JS, jQuery plugins?