Is this the same server as described below? If so, mono goes with Duplicati. It’s what runs the code.
Who provided the Duplicati Docker? I don’t use Docker, but generic mono TLS troubleshooting info is
Secure Socket Layer (SSL) / Transport Layer Security (TLS). Note mono has its own certificate store. Prebuilt images “should” take care of that. If you’re building your own, that’s something you must do…