Thanks @Sebahat.hadzhi for your reply. However, the root cause is clearly demonstrated by these two tests on my server:
The remote FTP server (Freebox NAS) responds 504 Unknown AUTH type to AUTH SSL and only accepts AUTH TLS. Whatever happens internally with ftps://, it fails on this server...
Full description:
Plesk Obsidian 18.0.77.2 (Ubuntu 20.04 x86_64, build date 2026/04/16)
Problem: FTP backups to an external FTP server (E.g. Freebox NAS) fail with the following error:
Investigation: Using auditd, I captured the exact command that pmm-ras builds internally:
When...