Is there a possibility to define the used protocol (http, https, file, ...) to load further resources manually? In my case several devices are using file:// as standard protocol... leading to IQ not working at all.
IQ was not designed to work over the file:// protocol, and although it is technically possible to edit the files to call a specific protocol, I would strongly advise against doing this, because you would have to edit every tag, and would end up in a difficult situation where you can't update to a new tag template without modifying it and merging in your previous alterations.
There are several scenarios where you might find a "file://" protocol, such as Smart TV applications, Cordova/Phonegap/Ionic apps, and some other applications. Which category does your use case fall into? If it's a Cordova-based app, we have a plugin that I strongly recommend you use. If it's a Smart TV application, the best solution is to use an iframe to load Tealium IQ, and pass tracking data to the iframe directly. Let me know your exact use case if possible, and I can point you in the direction of the best solution.