This seems to be a little mystical, some got it going, others not. Aren’t they displayed at all or is it only the dynamic part which isn’t working?
For me it’s working and here are some tipps (all are related to OH2 installations. I have also used custom icons in my old OH1 days, but I couldn’t remember what I’ve done there to get them going… ):
Some people have said that the ios app only supports png icons (not svg). I haven’t checked this but I am using png and they do work.
You have to define png as default both for the Basic UI and the Classic UI. You can do that in the appropriate file or in PaperUI settings for the both UI bindings (I would suggest PaperUI). Otherwise svg would be the standard.
The custom icons have to be stored in conf/icons/classic/ (doesn’t matter if you use BasicUI or ClassicUI, both take them from this folder).
And sometimes it helps to use “clear cache” in the iOS app, or even reboot your OH installation.
For the use of dynamic icons, this is another story to be told…