It’s not strictly privacy-focused but The Goblin’s Notebook is designed exactly for your use-case. It has markdown, object connections, every object has a player visible setting, so your players can access known content while you keep secrets hidden. There’s a free tier, a mid tier at $1.50 and an unlimited tier at $3 dollars a month (managed via their patreon).
A lot of 3D printing patents from the 80s and 90s expired between 2010-2020, clearing the way for commercial 3d printers and a million innovations. I’d call them honorary 21st century inventions, since the patent holders squandered the technology in the 90s.
https://www.finnegan.com/en/insights/articles/how-patents-die-expiring-3d-printing-patents.html