Links which would attempt to open call app or preferred email service on desktop do not launch on mobile. I don’t know whether it is just me, but I try to hit a button (<a href …> link) on the mobile app and I’m not prompted to open with the call app. Likewise for emails.
Additionally, though a separate issue, the tooltip on circular 
icons do not appear when pressed. Again, not sure if it is a setting on my device, or a problem for everyone.