I figured out a cool workaround that doesn’t cost a penny!
Zwift works smooth as cream on the iPhone. I have an old iPhone 5s and a mid 2009 15" Macbook Pro.
The idea is that you mirror your phone on your computer.
Here are the instructions I found online:
Connect your iPhone , iPad or iPod touch to your Mac via a Lightning Cable. Open QuickTime on your Mac , and select File > New Movie Recording . A recording window will appear. Click the arrow next to the Record button, and select your iPhone from the dropdown menu that appears.
For sound select your phone from the Microphone dropdown. Press the un-mute button on the Quicktime screen.
You’re all set!
Hope this helps some folks out!