Unity unsupported shader on iPhone 6s

Question

I'm making a game for Android and iOS. It is quite a simple project so all materials use LWRP Lit shader. I was trying to make build on iPhone 6s and iPhone XR. On each my Android device and on iPhone XR it works well. But on iPhone 6s I get freeze with graphical artifacts just after the gameplay scene is being loaded.

In Xcode there are those errors:

At the begining:

ERROR: Shader Shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
WARNING: Shader Unsupported: 'Hidden/Lightweight Render Pipeline/ScreenSpaceShadows' - Setting to default shader.

ERROR: Shader Shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
WARNING: Shader Unsupported: 'Hidden/PostProcessing/Debug/Waveform' - Setting to default shader.

ERROR: Shader Shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
WARNING: Shader Unsupported: 'Hidden/PostProcessing/Debug/Vectorscope' - Setting to default shader.

ERROR: Shader Shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
WARNING: Shader Unsupported: 'Hidden/PostProcessing/Debug/LightMeter' - Setting to default shader.

ERROR: Shader Shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
WARNING: Shader Unsupported: 'Hidden/PostProcessing/Debug/Overlays' - Setting to default shader.

ERROR: Shader Shader is not supported on this GPU (none of subshaders/fallbacks are suitable)
WARNING: Shader Unsupported: 'Hidden/PostProcessing/Debug/Histogram' - Setting to default shader.

At the end (in a loop)

Execution of the command buffer was aborted due to an error during execution. Ignored (for causing prior/excessive GPU errors) (IOAF code 4)

Right now I'm using Unity 2019.1.0a10, but previously I was trying to make a build with 2018.3.0.11b and 2018.2.17f1. I also tried few versions of LWRP but still the same result ;c

Screenshots:

Materials I use same settings for all my materials

LWRP Settings

Answer 1

I encountered the same problem. The shaders listed here (LightMeter, Histogram, etc.) are from the Unity Post Processing package. I actually switched my project to URP which has its own post processing so I just removed the old PP package and the assets associated with it and those errors dissapeared.

But it didn't solve the problem with graphical artifacts, which I also had. In my case, I had to disable the CullMode of the custom shader I was using, but I guess you need to dig deeper into your project's materials and shaders to see what the problem might be.