I just spent a lot of time looking this up and at various Reddit posts, and it seems like there aren't many alternatives for self-hosted syncing between Apple devices. Syncthing actually works fine for me, in fact one thing I like about Möbius sync is that since it stores files under "On My iPhone" / "On My iPad", I can access the folder in 3rd party apps, unlike 3rd party cloud services like Google Drive and OneDrive, that's an iOS restriction. I just want to compare it to other software for syncing without iCloud or another cloud service.