I would like to upload an e-book we prepared after two webinars, and simultaneously include a ResearchGate DOI. How do I get a DOI? It seems I can't find this option on ResearchGate.
Borrowing from Rob Keller: The best and most easy way to create a DOI for a paper of a journal that don't assign DOI number or chapters of previously published books without a DOI etc. is Zenodo: https://zenodo.org/
Please note: "ResearchGate DOIs can be generated for most of your unpublished work. As publications classified as article, book, chapter, patent, cover page, poster, and conference paper are considered to have been published elsewhere, ResearchGate DOIs cannot be generated for these types of research." (see the link indicated by Anton Vrdoljak )