Apple released Mojave yesterday and there were almost no problems. But one single computer is a bit choosy: the iMac 27″ from the end of 2012 with 3TB hard drive.
Installation cannot proceed with Boot Camp configured
As Apple writes in this Support document, it is not possible to install macOS 10.14 Mojave on this one model, if you have installed Windows via Boot Camp. To install Mojave you have to delete the Boot Camp partition before, otherwise you will get the error message:
Installation cannot proceed with Boot Camp configured
After that you can install Mojave again, but not Boot Camp. In short: You have to choose between Mojave and Windows via Boot Camp. If you still urgently need Windows for certain programs, you will have to virtualize using Parallels or VirtualBox, for example.
