I confirm the issue, but I'm not sure it's Flutter. I upgraded:
- Flutter to 3.35.4
- iOS to 26
- XCode to work with iOS 26

After that the debug version of the app became 100x slower to run. It takes about 5 min to run on my phone and it's almost impossible to use it after the start. It seems to be only affecting the dbug version. The release version works as expected.

It's hard to provide any code here. It happened for all my apps in iOS.