Use case or problem
See this help post for the details: How to get obsidian to show up in the iOS "share tray" for PDFs
TL;DR - many of the file types that Obsidian supports do not allow for adding to Obsidian via the iOS “Share Tray”, which requires custom shortcuts to be built.
Proposed solution
Please register additional file types (or even all files) with your Obsidian iOS app, so that Obsidian can be selected as an app in the iOS share tray.
Current workaround (optional)
See this help post for the details of my workaround: How to get obsidian to show up in the iOS "share tray" for PDFs