Define criteria on all pages (#1980)

docs/notebooks.en.md

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     [:octicons-info-16:](https://orgmode.org/manuals.html){ .card-link title=Documentation}
     [:octicons-code-16:](https://git.savannah.gnu.org/cgit/emacs/org-mode.git){ .card-link title="Source Code" }
     [:octicons-heart-16:](https://liberapay.com/bzg){ .card-link title=Contribute }
+
+## Criteria
+
+**Please note we are not affiliated with any of the projects we recommend.** In addition to [our standard criteria](about/criteria.md), we have developed a clear set of requirements to allow us to provide objective recommendations. We suggest you familiarize yourself with this list before choosing to use a project, and conduct your own research to ensure it's the right choice for you.
+
+!!! example "This section is new"
+
+    We are working on establishing defined criteria for every section of our site, and this may be subject to change. If you have any questions about our criteria, please [ask on our forum](https://discuss.privacyguides.net/latest) and don't assume we didn't consider something when making our recommendations if it is not listed here. There are many factors considered and discussed when we recommend a project, and documenting every single one is a work-in-progress.
+
+- Clients must be open-source.
+- Any cloud sync functionality must be E2EE.
+- Must support exporting documents into a standard format.
+
+### Best Case
+
+- Local backup/sync functionality should support encryption.
+- Cloud-based platforms should support document sharing.