I’m iPhone & Pop_os! . There are some obsidian forum threads that can help, I think this is the one that I used for my setup (1).
It is not completely obvious in the UI, but the basic idea is that you use a iOS git app (I use the excellent Working Copy) to just push and pull everything to GitHub, working around some inherent iOS limitations. As a bonus, you can setup the Shortcuts app to auto push and pull with closing and opening obsidian. There’s a git sync extension for obsidian, makes it all pretty seamless once it’s set-up.
If you choose to straddle ecosystems there really isn't that much that the likes of Obsidian can do to help though (especially when it comes to iPhone). I use Obsidian with Mac + Android (Synced via Dropbox, and backed up using git) and it works. Little bit of manual setup, but I can handle that.
At the end of the day Obsidian is just a directory structure of Markdown files. If needed, you can edit them with Obsidian (say using the Dropbox app).
You set up all your vaults under the same folder. You 2-way sync that folder to a cloud folder- Dropbox, MEGA, sync, box- whatever. You then create a folder with the same name on another device, and then use the client for your cloud service for that platform, and then set up two way sync with that folder on the cloud.
Works great with my Android-PopOS system.
Also tried it with Android-macOS, and iOS-Windows.
It is not completely obvious in the UI, but the basic idea is that you use a iOS git app (I use the excellent Working Copy) to just push and pull everything to GitHub, working around some inherent iOS limitations. As a bonus, you can setup the Shortcuts app to auto push and pull with closing and opening obsidian. There’s a git sync extension for obsidian, makes it all pretty seamless once it’s set-up.
1. https://forum.obsidian.md/t/mobile-setting-up-ios-git-based-...