Current bookmarking tools either lock data in walled gardens or sell user attention.
Build an open-source, self-hostable alternative with: markdown notes, PDF archiving, and relationship mapping between saved items. Charge for premium storage and sharing features.
Target academic and investigative teams who need to preserve source materials securely.
Start with a basic Chrome extension that saves to local Markdown files.
Risk: Hard to differentiate from established note apps without network effects.