Searching I found this post in the forums: Ride App Crashing on Start: iPhone 6, 8 and 10! - #2 by Tom_Frohna_MKE
I confirmed I was able to use app by: 1) just watching, 2) menu, 3) hit bluetooth icon on right, 4) connect, 5) back to me
Would be great if Zwift could at least surface the workaround via twitter and other mediums.