We're working to resolve this incompatibility on the Unity side, but in the meantime in order to use Xcode 14 beyond beta 2, you can use this workaround:
In the generated Xcode project (Unity-iPhone for now), select the project itself to get to the project settings.
For both the UnityFramework product as well as the Unity-iPhone app product, select the product, then click on "Build Settings" at the top.
Search for "OTHER_LDFLAGS". In the "Other Linker Flags" setting, add "-ld64" at the start.