I can't exactly recommend to use Amazon services, but if you're doing it anyway something like s3fs-fuse [0] should do the trick so that S3 appears as a standar

I can't exactly recommend to use Amazon services, but if you're doing it anyway something like s3fs-fuse [0] should do the trick so that S3 appears as a standard filesystem to syncthing. [0] https://github.com/s3fs-fuse/s3fs-fuse https://github.com/s3fs-fuse/s3fs-fuse