Long time Deezer Premium subscriber but only recently started using it on an iPhone, having come from Samsung. One difference I noticed in the iPhone app is that long pressing a track, say in a list of tracks for a particular album or playlist, does nothing like it does on the Android app, where it brings up a menu of everything that can be done with that track, including Play Next or Add to Queue. Instead you have to hit the three dots on the right, which is less convenient, especially while in a car or on the go.  
 

Strangely, long pressing on a track in the Now Playing section in the iPhone app DOES bring a menu of actions. This is inconsistent with the way it looks and works when looking at tracks in an album or playlist (and in Android).  And what’s worse, Play Next or Add to Queue are not among them as they are in the other view and in the Android app. (This is useful if in the middle of a long playlist so you don’t have to drag songs around to hear an earlier one again next or later.)

One other thing, when there’s a long list of songs in a playlist, for example, and you hit the button to view Now Playing, you can’t see which song is playing if it’s off the screen unless you scroll down to where it is.

Overall, UX/UI inconsistencies make ann otherwise incredible service and app a far less consistent and awkward experience compared to say Apple Music where everything works consistently both internally and compared to the Android app.