[Error-Duplicati.Library.Main.Operation.FilelistProcessor-BackendQuotaExceeded]:Backend quota has been exceeded - (0 bytes available)

Support
5

Glad you aren’t getting the error any more, but you do need to upgrade your mono version. Duplicati 2.0.5.1 requires at least Mono 5.x.

https://www.mono-project.com/download/stable/#download-lin-ubuntu