FreeFileSync Forum

Figured it out for anyone interested -- it wasn't an APFS issue, APFS seems to be supported in FFS. I was having problems with hidden .AppleDouble files. FFS doesn't seem to like these. They're created by MacOS on some external drives -- seems to be related to metadata storage (happens more on NAS ...

I (probably stupidly) formatted a new 8TB backup drive as the new APFS format that comes with MacOS High Sierra, and have already done a huge amount of data transfer there I don't want to repeat due to reformatting :)

It appears APFS isn't supported yet in FFS. In which case, I'd like to request it ...