The --dangerous flag is required because Canonical has not reviewed the package. The --classic flag allows Obsidian to access files outside the sandbox, where your notes are stored.
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Open Obsidian
Launch Obsidian the same way you open any other application.
On Chromebooks, the libnss3-dev package must be installed, otherwise you may receive the error error while loading shared libraries: libnss3.so: cannot open shared object file: No such file or directory.
The first time you open Obsidian, you’ll be prompted to create or open a vault. If you want to explore the app before setting up your own vault, open the Sandbox vault — a pre-built vault that showcases Obsidian’s core features and formatting options.
The sandbox vault is a great way to explore Obsidian without touching your own files. Any changes you make to it won’t affect your personal notes.