@Stork:
I've got an odd problem, and it's directly related to APFS.
I have a Gigabyte Z370 and the drives on it are HFS+. It's on 10.13.6. If I try and format any drive for APFS, I can't. The format won't complete and the drive is left in an incomplete state and won't mount. If I use my X99 that is 10.13.5 and is also now APFS, I can backup (from a HFS+ drive volume) and restore onto an APFS drive (formatted on the 10.13.5 system), but it won't boot on the Z370. My old least favorite error: HID legacy shim. Remember, HFS+ drives boot fine.
Now here's what's strange. I also have an X99 board that was HFS+. It's on 10.13.5. I converted all drives to APFS, using the process listed above - just reformat the system drive as APFS, then do a CCC restore from an HFS+ volume (at first). No issues, boots fine. In fact, my backup clones I converted just like as I've described, and they all booted. No issues.
So, I have a real Mac, and its on 10.13.6. I took one of the portable drive clones (USB) and plugged it in there and formatted it there as apfs, and it completed properly.
Right at this moment, I am doing a restore from an HFS+ volume via CCC to the newly Apfs formatted USB volume, the same process I used successfully to convert all the drives on my X99 system to APFS. I'll let you know if it worked, and if I can boot an APFS drive running 10.13.6 on my Z370 (or not). I'm beginning to believe there really is some issue with APFS and this Gigabyte Z370 board (and yes, BIOS is up to date).
But I now have a more serious problem. Clearly, I have an issue with my Gigabyte Z370 Hackintosh, as both my X99 Hackintosh (on 10.13.5) and my real Mac (on 10.13.6) will format a drive as APFS successfully, but my Gigabyte Z370 will not.
Thoughts? Anyone else have this issue?