Greetings! How do you convert an HDD over to APFS after upgrade? I have a single, standard SATA hard drive in my 2011 MBPro, and of course the in-place upgrade to High Sierra did not auto-convert it over to APFS. I went to Disk Utility, but the "Convert to APFS" was grayed-out (unusable). I booted my MBPro to the Recovery mode, and "Convert to APFS" is still grayed-out. So what's next for me to try to get my High Sierra over to APFS, without having to lose data or reformat/restore data? Thanks!