Zotero is a "personal research assistant" that can help you "help you collect, organize, cite, and share research".

It used to be available in Debian up to "stretch" but was removed from Debian "buster" after the Firefox 60 upgrade which broke the extension (864827). While work is underway to pacakge the new 5.x version (871502), there are other alternatives to run Zotero in newer Debian releases.

Flatpak

The Flathub maintainers provide a Flatpak package that can be easily installed in Debian buster:

flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
flatpak install flathub org.zotero.Zotero

Then Zotero can be ran with:

flatpak run org.zotero.Zotero

Or by adding /var/lib/flatpak/exports/bin to your PATH:

echo 'export PATH=$PATH:/var/lib/flatpak/exports/bin' >> ~/.bashrc

In my experience (TheAnarcat), the "flatpak" Zotero was able to read the previous database directly without problems, but you might have to do some tweaks in the flatpak config if it's in a non-standard location. This is explained in the flathub page.

See also the FlatpakHowto.

Snap

There is also a Snap package but it does not seem up to date.

Standalone install

You can also download the official release and install it by hand.