What backup strategy for local computers should I choose?

Question

Backup

Hello. I can not decide on a strategy for backing up information from users' computers. Given: working group, peer-to-peer network. Required: to ensure the recovery of information (mainly documents, tables, images) in case of force majeure, i.e. failure of the hard drive, the operation of the ransomware, etc. Previously, Synology NAS took care of backups. The Cloud Station Backup application has been installed on user PCs, in which you can select folders for synchronization with the server. For example, the synchronization included the Desktop, Documents, Images, and during the day the information from these folders was automatically synchronized with the server, and at night the data from the synchronization folders was backed up by the NAS to the second disk (Hyper Backup), creating an actual snapshot of the information for the day. Depth adjustable, i.e. You can always extract information for any previous day. The snapshot size was the size of the changed data per day, i.e. disk space was not expensive. Then the NAS stopped coping and the synchronization task was transferred to a server with Nextcloud installed, the client application of which synchronized selected folders from the local computer, and the creation of nightly snapshots for the previous day was done using rdiff-backup by cron. Now it is required to provide a similar scheme, but without the participation of Nextcloud, i.e. you need a synchronizer program that can maintain the identity of files on the server and client computers in real time. Are there analogues or is the concept of backup itself wrong and needs to be changed? And if so, for what? disk space was not expensive. Then the NAS stopped coping and the synchronization task was transferred to a server with Nextcloud installed, the client application of which synchronized selected folders from the local computer, and the creation of nightly snapshots for the previous day was done using rdiff-backup by cron. Now it is required to provide a similar scheme, but without the participation of Nextcloud, i.e. you need a synchronizer program that can maintain the identity of files on the server and client computers in real time. Are there analogues or is the concept of backup itself wrong and needs to be changed? And if so, for what? disk space was not expensive. Then the NAS stopped coping and the synchronization task was transferred to a server with Nextcloud installed, the client application of which synchronized selected folders from the local computer, and the creation of nightly snapshots for the previous day was done using rdiff-backup by cron. Now it is required to provide a similar scheme, but without the participation of Nextcloud, i.e. you need a synchronizer program that can maintain the identity of files on the server and client computers in real time. Are there analogues or is the concept of backup itself wrong and needs to be changed? And if so, for what? whose client application synchronized selected folders from the local computer, and the creation of nightly snapshots for the previous day was performed using rdiff-backup by cron. Now it is required to provide a similar scheme, but without the participation of Nextcloud, i.e. you need a synchronizer program that can maintain the identity of files on the server and client computers in real time. Are there analogues or is the concept of backup itself wrong and needs to be changed? And if so, for what? whose client application synchronized selected folders from the local computer, and the creation of nightly snapshots for the previous day was performed using rdiff-backup by cron. Now it is required to provide a similar scheme, but without the participation of Nextcloud, i.e. you need a synchronizer program that can maintain the identity of files on the server and client computers in real time. Are there analogues or is the concept of backup itself wrong and needs to be changed? And if so, for what? Are there analogues or is the concept of backup itself wrong and needs to be changed? And if so, for what? Are there analogues or is the concept of backup itself wrong and needs to be changed? And if so, for what?