have you looked into a Scriptable script for downloading all critical iCloud files before flying?
One of my main requirements for an app is that it does what paper cannot do. I can use paper if I step out of my house. An app that cannot be used offline is an app I cannot use if I am not at home or at a place with secure wifi, and therefore violates the “cannot be done with paper” principle. You may think differently, and that’s ok. But lack of offline support is still a valid reason not to use Notion or any other software.