Searching digikam
To find notes about the digikam setup — database location, SQLite schema, collection paths, sidecar settings, search queries, or anything else digikam-related — use islandiguana to retrieve all vault notes tagged digikam:
/Users/mtm/go/bin/islandiguana "/Users/mtm/Documents/Obsidian Vault" '.tags[] == "digikam"'
Read the returned notes.
They contain the authoritative information on where digikam stores its database, how to query it, where collection roots are defined, and how to search media.