Beorg is a pretty good implementation of Org-mode on iOS. The latest version introduced a couple new sync options and much better editing features.

My problem is that I keep my Org files in ~/org on my Mac and sync them between machines using Syncthing. I don’t want them in Dropbox or iCloud, but I’d probably choose iCloud first. What I haven’t figured out is how to nicely create a symlink to the ~/org directory in the iCloud Drive directory. None of the crazy paths I’ve tried seem to work. I suppose I could go the other way and make ~/org a symlink into iCloud but I’d rather go the other way. Any ideas?