Run flutter app in IOS Simulator with Xcode in RELEASE mode On a Cloud hosted Mac

Result : Error – IOS simulator does not support release mode.

PS : I tried this,
Build Flutter app in release mode for iOS
but then my build breaks.
Error : Command PhaseScriptExecution failed with a nonzero exit code

I can’t find another option because I am using a rented Mac which is hosted in Switzerland.
What can I do to test my IOS device in release mode?

I have an Iphone but no way to connect it to the Macbook because the Macbook is hosted in the cloud.

So when I test the code in the simulator it works. But when I push to production it breaks and I get an empty grey screen.