Back up an Obsidian vault to GitHub on iPhone
An Obsidian vault is a folder of files. If your vault is accessible under On My iPhone and Obsidian can keep using that location, Local Git can link it to a writable GitHub repository.
How to use it
Confirm the vault location
In Files, check that the vault is under On My iPhone and that Obsidian can open and edit it.
Prepare a GitHub repository
Use a disposable vault and repository first. Linking an existing nonempty folder may replace its contents during clone.
Link and synchronize
Connect the repository in Local Git, make a test edit in Obsidian, then review and synchronize the change.
Check the fit
This is manual Git synchronization, not continuous backup or Obsidian Sync. Do not run two sync systems on the same vault without understanding their conflict behavior. iCloud Drive vaults are unsupported.
In short
Local Git can synchronize a local, Files-visible Obsidian vault with GitHub when both apps can use that folder. Test the exact vault setup before relying on it.