Hey there,
My question is whether or not its possible to use Ionic without any of the UI? E.g without angular, or anything specific to the front end Ionic stuff.
The reason for this, is we are trying to get a better performing version of Cordova and have already developed our own UI framework based in VueJS.
As of now, attempting this results in a ‘white screen of death’ on the emulator which is proving impossible to debug.
Ionic is UI + Angular + Cordova. So if you replace the UI and Angular, you are left with Cordova again 
(Yes, it’s really just 100% pure Cordova, no special Ionic changes)
For your problem: Did you remote debug the problem on the device already?
Follow these instructions here to debug the problem in Safari dev tools: https://ionic.zone/debug/remote-debug-your-app#ios
Follow these instructions here to debug the problem in Chrome dev tools: https://ionic.zone/debug/remote-debug-your-app#android
Look at the console and network tabs for errors.
I think you have to develop your own UI within cordova and watch every step…
Even a slight error will freeze the whole app.
You can try to use Apache Cordova or PhoneGap which ship without any UI framework & angular.
To be more accurate, Ionic = Ionic UI + Angular + Ionic CLI + Cordova.
So without UI and Angular, we still have Ionic CLI + Cordova.
In one mobile app I recently developed, I used other Bootstrap-like UI framework, but used Ionic CLI for the dev and testing process. Ionic CLI is more convenient than working directly with Cordova.