Handle deeplinks into your Ionic/Cordova apps from Universal Links, App Links, and Custom URL schemes. For those using Ionic 2, there are some nice goodies that make life easier.
I found the issue is in index.d.ts line 2. In Observable import statement.
It should be ´import { Observable } from 'rxjs';´ instead of ´import { Observable } from 'rxjs/Observable';
I also saw a similar error with @ionic-native/deeplinks version 4.10.0.
In my case, it was fixed by updating @ionic-native/deeplinks to 5.18.0. (And change Deeplinks import path)