I'll make an request for keeping the userdata behavior local first as a core value. A second brain should be owned by the user (sorry Roam) and not restricted by things like availability of a data connection (Sorry Notion) or a specific tech stack (sorry Org Mode). If it can be reasonable operated on by user usertools like grep that other search tools are build on, then navigating and using the second brain should still work 20 years down the line.