Free Apps (Online & Offline) which are Capable of Being Brain2

The new definition of brain2:

• Brain2 = Graph of Trees or Structs including lonely Nodes
• Requirements for app: Graph, with structural UI (not autolayout)
• Optional features: Convenience is better.

Here is the comparison of FREE apps both online and offline which can be used as brain2:

• RemNote: With graph, structure is also content, very convenient
• Specific point: Can store large amount of data
• Cons: No E2EE encryption, can't pin nested docs (work-around: pin nested docs to a top-level doc as Refs)
• Pros: ESE (easy structural edit with tab/shift+tab). Additional structure on left panel for overall view (outline view) Outline view is important to see structures of multiple items at the same time.
• LegendApp: With graph-like only (mirrored items), structure is also content, very convenient
• Specific point: For small amount of data only, each top structure is a file
• Pros: ESE (easy structural edit with tab/shift+tab). With E2EE encryption
• Dynalist: With graph-like (thru' Ref), structure is also content, very convenient
• Pros: Can pin nested items, but no overall structural outline on left panel.
• Cons: RemNote has more features
• Anytype: With graph, structure is also content, not convenient UI
• Pros: E2EE encryption
• Cons: No easy-structural-edit, need to switch to a node to create children while RemNote and LegendApp can tab/shift+tab to create multiple levels of nesting docs inside.

These apps are without graph, or graph-like, or work-arounds to make it similar to graph

• Standard Notes: 
• No structure (pay-to-use)
• Joplin: 
• With graph of notes but the structure is tree of notebooks instead of notes
• Notion: 
• Work-around to make graph by linking notes but no structure shown, the note-subnote structure on left panel is not containing that graph by linking notes
• Obsidian: 
• Is a plugin for VS Code not separate app
• Evernote, OneNote, Google Keep, Amplenote

These guys are based on file per note and notes are not linked together to make graph or structures

• Dropbox Paper, Proton Docs

These guys are free but the limits are too small to use

• Workflowy

Some minor apps author hasn't tried out

• Simplenote