Recommend Backup Server Solution for Noob

DietPi appears to offer the best platform for running a Raspberry PI 1 B (512mb ram) as a backup server. However, DietPi seems to offer a lot of options. I’m hoping the community could narrow down my options with the following desired options:

  1. Simple install and set up using the above Pi with an external powered USB drive.
  2. Clients for both Windows and Linux (mixed environment)
  3. I don’t need Android or OS support, but it would be nice if I could remotely connect from my work computer (even if this is by ssh) to grab a few files every once in a while.
  4. NICE but NOT NECESSARY: Reversion copies can be configured (As in fileA.txt is kept on server with revision 2 and 3, then version 1 is deleted when the 4th reversion is saved).
  5. Website like Dropbox interface is not necessary, but it would be nice to be able to see the files through ssh session.
  6. It would be nice if I could use a USB drive that already has data on it, and would not have to format it as ext4, but this is not a deal breaker either.

What does the community recommend for an older Raspberry PI and offering some of the above features? I’m a little overwhelmed by all of the options: Nextcloud, Pydio, UrBackup, Samba, etc.

In searching the forum I found the following post, but it doesn’t seem to make any recommendations or conclusions in the forum thread or Google Doc:

There are a few options, Personally i would go with a simple NFS and then use software on the client machines to backup to the network drive.