Zotero is a free, open-source reference manager designed to store, organize, share, and cite bibliographic references. It comprises a desktop application, browser connectors, and word processing integration.
Zotero is compatible with most web browsers and can be used to insert citations into documents using:
LibreOffice / OpenOffice
You do not need to sign up for an account to use Zotero, but registering will allow you to create shared groups and to sync your citations across devices and online. Zotero is free to download and use; the only cost is for optional additional online file storage. As of February 2022, the first 300 MB is free.