Something like Rclone and a cron job, or else s3 mounted via FUSE, could possibly bridge that. Of course then you have to worry about reliability of the bridge...
There’s support via Barman cloud - we use it for azure at work but s3 and others are supported iirc
https://github.com/Barre/ZeroFS Should do a great job at this.
Mounting S3 with Fuse is not stable or performant enough at scale for backup storage