> Try to set up a hotspot, there is no button to turn the hotspot on/off.

There is. You can even put it on the settings drawer. Look for "personal hotspot".

I don't have a mac anymore, but IIRC you could even turn it on from the paired mac. This definitely still works between iphones. When I take out my old iphone from the drawer to use as a GPS on my bike, with no sim card, it will connect to my regular iphone's hotspot automatically.