Hi,
I'm facing same issue. I found some solutions, one is using 2 Macs. The first one is connected to the iPhone (which is connected to the internet) and the 2nd one is connected to first Mac which shares its network connection.
I find another solution : GL.iNet GL-SFT1200 (approximately 40€).
This small router can be used as a wifi repeater and ethernet switch. It can share smartphone connection through usb port also but I didn't test it yet. I connected my Mac with ethernet, I shared my iPhone network with wifi and it worked, Photo library on my Mac has uptaded.
Nico