I am using this procedure for regular backups: https://firebase.google.com/docs/firestore/solutions/schedule-export
and some tooling to locally analyze data in the resulting (downloaded) LevelDB backups.

The Admin SDK exposes (internally, but still) createTime, readTime and updateTime properties on snapshots. I don’t see these properties included in the database exports; which makes them less complete as backups, and less useful for data analysis.