I was surprised at how similar Trilium looks to Obsidian when it was suggested in a thread somewhere: https://triliumnotes.org/ https://triliumnotes.org/ It's

I was surprised at how similar Trilium looks to Obsidian when it was suggested in a thread somewhere: https://triliumnotes.org/ https://triliumnotes.org/ It's open source and as far as I can tell uses a database.