Using r.Shaders.Optimize=0 with native metal libs results in a crash of the packaged build at runtime.
Workarounds is to either not use native metal libs for text shaders or in MetalShaders.cpp comment out the lines:
This needs a bit more investigation to before making changes so raising this bug.
1. Sync SunTemple project with engine.
2. Run GenerateProjectFiles command
3. Open workspace in Xcode and in ConsoleVariables.ini set r.Shaders.Optimize=0 for text shaders
4. Compile and run the editor load the SunTemple project.
5. Package for iOS or MacOS.
6. Run packaged build observe crash.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-90756 in the post.