I used Borg for years and it's good, but the fact that you can only backup to SSH is quite limiting. I eventually found Restic & Rustic which are much better and support way more backends:
https://rustic.cli.rs/docs/comparison-restic.html#supported-...
Can't you transfer the resulting archive however you want? rsync, ftp, USB stick glued to a bird, tattooed onto a shaved man's head, etc?
Borg 2.0 (unreleased) is moving in a similar direction with borgstore:
https://www.borgbackup.org/releases/borg-2.0.html