I hope this helps those who struggle to use Obsidian on iPhone. I know many people use 1Writer, but I made a faster and cleaner solution with an iOS Shortcut. In this way, you can capture thoughts into Obsidian anywhere using iPhone or iPad.
My shortcut simply prompts you to write a note and then saves your note as a normal text file into your iCloud Drive. Finally it changes the extension of this file to Markdown format and deletes the original text file. It syncs instantly to Obsidian.
The best part is that you can then have a shortcut on your homescreen for very fast capturing. The downside is that you won’t be able to change or add to notes (like with 1Writer), only add new notes.
Full setup guide here: Take Quick Notes in Obsidian from iPhone