I use borg indeed, via Vorta. Also, I am a rsync.net customer (I think you should start with a smaller min storage for pay what you use, or keep it pure pwyu).

I am looking for another backup tool that backs up to an S3 storage destination and has a decent GUI (restic doesn’t have a GUI; relica doesn’t count; and borg doesn’t support s3). Since rclone has an experimental GUI I wondered.