When launching on iOS 8.4 simulator the following error breaks JS execution early on:
ios-wkwebview-exec.js:127 TypeError: undefined is not an object (evaluating 'window.webkit.messageHandlers')
So inclusion of 'cordova-plugin-wkwebview-engine' plugin breaks support of iOS versions previous to 9.0. I assume ios-wkwebview-exec.js should have environment checks before using WKWebView bridge...
Exclusion of the same plugin breaks the project at all. Are there any fallback mechanics in place?