To give some more specifics, just from the top of my head:
* The desktop client is basically incompatible with GNOME (you know, by far the most common DE on Linux) since it relies heavily on indicator icons which don't exist on GNOME
* Under Wayland, when clicking the app icon, its window appears at some random place on the screen instead of under the icon
* When playing audio through the iOS app, you often end up with two audio tracks playing on top of each other