Zotero
Zotero is an open-source bibliography management tool. I started using Mendeley during my phd, when I wasn't yet considering choosing technology based on their incentives.
Zotero allows you to define collections (groups of papers), parses the metadata of the papers and downloads information from some predefined data sources.
Their business model is subscription-based in case you want to synchronise your library on different devices.
You can also create shared libraries and give access to your colleagues. I didn't find the feature particularly useful, since you very quickly loose control on what is being added.
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