I ended up taking my external HDD and plugging it into a Windows 10 computer, using Disk Management to convert to GUID and then tried to convert the drive to APFS.

(See below, it used to look like this before High Sierra, but now the third option is gone) (I've submitted a request to Apple for them to put it back in).

(after an hour of trying different things).įrom what I can see High Sierra Disk Utility no longer gives the options of choosing a scheme (GUID vs MBR) when formatting a drive. Obviously this solution required Linux, so hopefully there is a Mac-only alternative. The T5 mounts, identifies as APFS and passes Disk First Aid as an APFS volume. Interestingly, Disk Utility first automatically formatted the drive as HFS+ and continued on to APFS. Selecting the T5 I was able to Erase this drive as APFS. NOTE: The unallocated T5 did not appear in Disk Utility until I used the Show All Devices command in the View menu. As is normal, the Mac reported that this drive was not usable and offered to Initialize. With the T5 showing in Gparted as entirely unallocated, I removed it from Lubuntu and reattached it to the High Sierra Mac. While Gparted immediately offered to reformat the drive with a Linux file system, I simply declined any formatting. I did this using Gparted, the well-known Linux disk management utility, running on Lubuntu - this of course on a Linux computer. I have solved this problem by removing all formatting and partitions from the T5.

Format samsung t5 for mac