Gen A?

I can recommend duplicati on windows or pika backup (which is a borg backup gui) on linux. Then just make a user on raspberry pi and enter the ssh login in your backup client and you’re set.

Duplicati / Pika / Borg will encrypt the backups for you! So there is no danger of someone reading or changing your backups. You could use even some free cloud storage to store the backups safely. It really doesn’t matter where you store them.

Rsync won’t deduplicate or make archives so you cannot restore a backup from any chosen date. Rsync is sync not backup.