Flutter debugging on iOS

I've only ever built Android/Web apps with Flutter, but I had a request to get one of my apps working on iPhone. I knew I wasn't going to have fun before I started, and I wasn't wrong. But I managed to get an Apple Developer Account, jump through the hoops for adhoc distribution profile and certificates, built an account at Codemagic and succeeded to get build to work, managed to downgrade Flutter until I could get an iOS 12.0 build to install on an iPhone6, but now it fails when it loads and I have no clue how to troubleshoot this.

If it were android, I'd have it hooked up to my dev station and run debug version to monitor, but this inscrutable chunk of plastic and glass doesn't seem to work that way. I don't have a Mac box to dev on, so I'm left with running CI builds that I pull down via Diawi to the device, but it's a black box from there.

Is there a way to do anything useful on a Linux dev station with these things?

God, if Google's "developer registration" is anything like this nightmare, I'm going to work on helping dev a Linux phone fulltime.