My backup is growing and growing and I was looking for cheap off-site (cloud) storage with sftp access for Duplicacy.
The result is this list:
It contains affiliate links but I will also add providers which do not offer an affiliate program (e.g. Hetzner).
If you find a provider which is under 20€ / 1Tb / Month and offers sftp or webdav you can post it here and I will add it to the list.
I also created a tutorial for windows users on how to use ssh certificates: