I can confirm that Mojave runs under HFS+. How I did it: 1. Downloaded the 1st developer beta and installed over a working copy of High Sierra. This converted the partition on the [platter-based] hard drive I used to APFS. 2. I then updated the install to beta 2 using Software Update. Still APFS. 3. I used SuperDuper to clone the result to an SSD initialized to HFS+. 4. SuperDuper cloned the install from APFS to HFS+ without problems. 5. I booted from the SSD, up-and-running now. Disk Utility sees and reports it as "Mac OS Extended (Journaled)", NOT as APFS. So... it can be done. Notes: This is one time that CarbonCopyCloner failed me. It WOULD NOT do the job, would not permit me to select either source or target drives. Don't try this [yet] with CCC. SuperDuper came through. I will note that on my first attempt, SD seemed to hang trying to do a "snapshot", or whatever. So I force-quit it and tried again. This time SD breezed right over that step, and then went on with the clone. My impression is that the only reason there's no pathway to install Mojave to HFS+ is because Apple wants to force us into APFS. Brings to mind how Mail.app tries to force the user into IMAP during initial setup, with no apparent way to set up a POP account. I'm not sure what will happen with the next beta release. I'm wondering if software update can update the HFS+ volume "as it is". Will have to wait and see. But you -can- keep using HFS+ with Mojave, if that's what you want.