Hi Gerold,
The advice against cloud storage has to do with managed cloud folders like DropBox, OneDrive and Google Drive. They have rather primitive management of multiple access and don't provide any information to Help+Manual about multiple users accessing them at the same time. The result is that you end up with multiple "conflicted copies" of the same files, with different editing status in each copy. It's then impossible to put together a version that really reflects the current status you wanted to get. In addition to this, in some circumstances you can also overwrite each other's work completely. OneDrive is particularly bad for that.
The software I recommend for automatic backups is calld AJC Active Backup, by a Help+Manual user called Andrew Cutforth:
https://www.ajcsoft.com/active-backup.htm
It's a brilliant, inexpensive tool that just sits in the background and makes ongoing backups of all the changes in the folders and file types you tell it to monitor. The backup increments only save the differences and are compressed, so they are very compact. I just have them go to my Synology NAS (also highly recommended). I can also only say good things about Andrew's AJC Sync program, which you can use to keep folders in sync with support for a huge range of different destination types. I use it for keeping backups of important stuff on Amazon AWS.