I also use Zotero which I really like because you can add tags and it also automatically detects some. You can also easily generate a bibliography with the right citation when you need to write a paper.
However, even though it is open source, the Zotero developers don't seem to be keen to help people to install the server-side on their server.
Welcome to Qowala's Mastodon instance!
Here, we love open source and we study and work on social networks so naturally we also host a Mastodon instance.
Friendly people are welcome, but as this is a small server, there are limited available slots. So, choose wisely to join or not.