Libre Contacts Backup is a FLOSS native Android app for private, local-first contact backups. No account, no cloud, no tracking — your contacts never leave your device unless you choose to move the backup file yourself.

Features:

Lossless backup preserving the full Contact → RawContact → Data hierarchy, including contact groups
SIM card phonebook captured in every backup; on restore, SIM contacts can be written back to the SIM card, into the device address book, or both — and on phones with more than one SIM (including an eSIM) you pick which of the available cards they go to
Scheduled local backups at a time you choose — daily, weekly on a selected weekday, or monthly on a selected day (if a month is shorter than that day, it runs on the month's last day) — with no internet connection required
Single-file LCB archives containing canonical JSON, VCF, CSV, and normalized exports
Optional AES-256-GCM password-protected encryption (Android Keystore backed)
Restore consolidates each source contact correctly, without merging different people who share a name
Manual CSV and vCard exports, and the CSV opens in Excel and other spreadsheet apps
Retention by age — keep the newest backups per day, week, and month with counts you choose (for example 7 daily, 4 weekly, 3 monthly), so the recent past stays densely backed up while older history thins out — or simply keep the last N sets

Libre Contacts Backup is free and open source. If you find it useful, you can support its development — see the donation options in the project README: https://librecontactsbackup.ashkanrafiee.com/#donate