Earlier quoted context omitted.
It’s difficult. iCloud works (but I don’t want to do that, because it’s not E2E encrypted). Copying manually via iTunes too. I guess the options will stay limited, as the author wants to sell his commercial sync service.
The limitations are purely on the iOS device. I am using Syncthing on iOS with Obsidian and no issues. Fully agree with wanting to avoid iCloud in all cases where one can. (Also, sidenote: assuming gender is maybe not necessary: his => their)
On a personal note, please don't do this. I understand people choosing their preferred pronouns, but don't force it on others unless they have stated preferred pronouns too.
Quick edit: went and looked at the developer team (https://obsidian.md/about). It's actually a man, a woman and two cats, so "their" is clearly appropriate.