@kboyd I did! It's EazyBackup's E3: https://e3.eazybackup.com/
I've only used it with restic, but it's working well, and their support has been *fantastic*. No idea about speed, I've only got 50Mbps up-stream right now.
If I calculated correctly, storage for my < 2TB of backups will be roughly the same cost as Backblaze B2, which is much cheaper than S3.