It all depends on your requirements, which you did not specify too clearly. Do you want online storage (web / dav / ftp / sftp) or storage on your own network?
If you are looking for a solution that is available for almost every OS and where the repository is located somewhere in our wonderful Internet verse, the solution could be webdav / s . I'm not sure if I understand the expression "FTP files that you yourself can assign." Please be a little more specific.
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