Nxs-backup is described as 'open source backup software for most popular GNU/Linux distributions' and is an app in the Backup & Sync category. There are four alternatives to Nxs-backup for a variety of platforms, including Windows, Linux, Mac, Microsoft Hyper-V Server and Online / Web-based. The best alternative is Acronis True Image. It's not free, so if you're looking for a free alternative, you could try UrBackup or Veeam Backup.
Acronis True Image (or simply True Image) is a software product produced by Acronis that provides data protection including, backup, archive, access and recovery for Microsoft, macOS, iOS and Android operating systems.
UrBackup is a open source client/server backup system, that through a combination of image and file backups accomplishes both data safety and a fast restoration time. File and image backups are made while the system is running without interrupting current processes.
Retrospect is a multi-platform backup solution supporting hybrid backup to disk, tape, NAS & Cloud, aimed at SMEs and MSPs. Main Editions include unlimited client/endpoint licenses. Site License Edition includes unlimited server licenses.