Trilium Notes

Trilium Notes is a hierarchical note-taking application built for extensive personal knowledge bases. It can be self-hosted and supports advanced features like note cloning, scripting, relation maps, and encryption. It's designed for power users who need to manage large amounts of structured data and want complete control over their hosting. It's free and open-source.

It scores for its impressive depth of features and self-hosting capability, catering to users with highly complex, technical knowledge management needs.