First up, Scrivener works great in iOS12 and macOS Mojave betas. In use all appears stable, syncs continue to work etc.
There has been one major problem with iOS, the Scrivener icon disappeared with the update and cannot be found. Open from the App Store works though Scrivener never appears on the recent apps.
In Mojave dark. mode native Apple apps also display in dark mode. Scrivener retains the standard view.
I realise Mojave is in beta, however hope if feasible Scrivener will also flip to dark mode with the system wide setting by the time Mojave is released.