first of all we would like to thank you for the quick babylonjs support we are getting, it’s really amazing! Also, congratulations on the 4.2 release
In our current project we are using transparent materials a lot and babylonjs does a really great job at rendering them with the depth prepass option. It works quite well on WebGL 2.0. On WebGL 1.0 iOS 14 however, rendering artifacts which look at lot like Z-Fighting appear when used in combination with a PBRMaterial and IBL. This is not specifically a WebGL 1.0 issue because by forcing WebGL 1.0 we are not able to reproduce this issue on other devices. These rendering artifacts do not appear with a StandardMaterial or without IBL. Enabling WebGL 2.0 Preview on iOS 14.0.1 also fixes the issue however this is not an option for production.
Test device with the issue: iPad Gen 7 iOS 14.0.1
Other WebGL 1.0 devices without the issue: iPad Air 2 iOS 13.3, iPad Pro Gen 3 iOS 13.3.1
Sandbox to reproduce the problem: https://www.babylonjs-playground.com/#1PLV5Z#35
Edit: iOS 14.2 has also the issue.