Thank to those 2 PRs:
We can turn off or turn on TM/Fabric. This repository is an example, where you can test this new functionality, which will be shipped in RN 71. It might make your migration much easier.
If you would like to turn off the fabric, please use the below approach:
Add additional parameters to a below method:
Override fabricEnabled and turboModuleEnabled inside AppDelegate.mm
https://github.com/troZee/RN0710RC4/blob/main/ios/RN0710RC4/AppDelegate.mm#L27-L38