Is the backup program suitable for the conditions?

Question

Backup

Greetings!
In general, finally, there was a server purely for backups.
I want to do everything "wisely", we have:
on the Ubuntu 14 server, on Windows 7-10 clients, the backed up files are mostly binary,
on the server I want access from clients only via sftp, 1GB channel.
therefore, a backup program is being sought, if possible with a UI so that users themselves can restore files (albeit not to their original location), on clients I would like auto-backup on a schedule and only changed files. Files are mostly from 300Mb. At the moment, backups are 8 TB. (month).
PS Preferably free =)

Answer 1

In general, I settled on Bacula

Answer 2

there are no free
ones more and more convenient paid

Answer 3

nnCron/nnBackup won't work?

Answer 4

Samba ball with traffic encryption on the server + built-in backup utility for clients.