How does one use this with something like a Synology NAS? Or is that not really the intended workflow? I’m imagining something like a local backup plus a backup to cloud.
If you want to backup just data, restic works very well; however, you're not backing up configurations or applications. Use HyperBackup. B2 S3-api is compatible.
I’m not 100% on which workflow you are looking to set up. If you are trying to backup to Synology NAS, you could mount the NAS and use rclone’s “local filesystem” storage backend.
I was thinking that I could use a readymade NAS (along with their software) to backup things locally but then I also want a secure and privacy backup of that NAS to a cloud.