I haven't used Nextcloud or Opencloud but I imagine their file management solutions are similar to Google Drive.
Paperless-NGX is like the "more advanced organization" option compared to Google Drive from my point of view.
Paperless allows you to ingest documents through a variety of means (upload button, watched folder, reading emails and automatically saving attachments or the email based on rules).
Then it tries to apply machine learning to extract the document date and other info like who the document is regarding, what kind of document it is, where it should be stored, all based on what you have manually added metadata for. If I have a receipts document type, it will learn what I consider a receipt and assign that automatically.
It also OCRs all the documents and stores the text so it's searchable later.
You can add custom metadata fields like a global document ID (I'm told).
You can then search, view, organize, share these documents in the paperless web UI.
You can customize how it stores all these documents on disk so you can still access them outside of Paperless if you want.
There are a few apps that allow direct "scan to paperless" functionality with decent cropping.
You don't scan documents so each page is a file. You ingest a PDF with multiple pages normally so you would scan with your phone or a scanner, then import to paperless. Though you can ingest images and other stuff.
