This is probably verging on paranoia, but I store Discourse backups on AWS S3 (which is supported out of the box) and then sync the backups from S3 to GCS using:
No programming required. This will increase your storage costs slightly, so it doesn’t help if you’re trying to save money. I keep the latest 10 backups, each are 10 GB, and it costs me $3/month at Google.