Back to My Mac will not be available on macOS Mojave. You can get ready now by learning about alternatives for file access, screen sharing, and remote desktop access.
This showed up as part of .Mac way back in the Mac OS X Leopard days. Apple hasn’t offered much of an explanation as to why Back to My Mac is going away, but the linked support document offers suggestions on how to replicate its features, including the use of iCloud Drive for file syncing, Screen Sharing for remote control over a local network and Apple Remote Desktop.1
- Yet another Apple application that hasn’t received major attention in years. ↩