SFTP backup extension error: unsupported DSA key size 2048

Symptoms

SFTP Backup extension fails to connect:

Failed to create the directory "example" at example.com: unable to make SSH connection: ssh: handshake failed: ssh: unsupported DSA key size 2048

Cause

This is caused by the product issue EXTPLESK-5635, which will be fixed in a future version of the extension.

Resolution

Consider using an alternative backup method if possible.

As a workaround, the directory /var/lib/psa/dumps (which contains local backups) can be backed up manually with the rsync utility, or similar.