https://www.onemodel.org aka OM: available and in daily use, but progress is slow until health improves. A highly effective (desktop) knowledge manager, text UI, Free (AGPL), using Scala and PostgreSQL (working to move to Rust). Something like an efficient combination of mindmap, zettelkasten and GTD in one, with much greater ambitions including for linking instances for collaboration; see site links to screen shots for some idea of how I organize/categorize things. Low-volume announcements email list available (under "community").