How have you liked Obsidian? I was going to use it but realized it pay walled sharing notes between devices. Looking into this again - are you self hosting Obsidian via LiveSync plugin?
Except I wanted more security and multiple users. Instead of using the default admin user, I created one user for each person. Done in the "_users" database. Then create one database for each person. Assign each user as a "Member" to their respective database, not admin. Now each person has their own credentials that can access only their database.
Not OP but I'm a very happy longtime Obsidian user. Maybe a little unfair to characterize as "paywalled" given their sync service is optional (and works very well), and a directory of markdown files is about as portable and flexible as it gets for self-hosting.
Except I wanted more security and multiple users. Instead of using the default admin user, I created one user for each person. Done in the "_users" database. Then create one database for each person. Assign each user as a "Member" to their respective database, not admin. Now each person has their own credentials that can access only their database.