Treedome is a local-first, encrypted, note taking application with tree-like structures, all written and saved in your computer
Currently you can only try it by building it yourself, instruction here. https://codeberg.org/solver-orgz/treedome/src/branch/master/docs/building.md But .deb and nixpkgs update is planned to follow suit though! You can also try an outdated one in https://aur.archlinux.org/packages/treedome-bin
Tell me what you think about it!
On the second point, Obsidian's vaults are intentionally stored as a single folder that can be synced easily, including all settings. They do have a service for syncing, but with a bit of tech know-how it's still really easy to sync. Also, all notes are stored as plaintext markdown files, which is convenient since many programs can read markdown.
Rest is correct tho.
Is it stored in a single folder like joplin does? Can I move the folder around and easily open it after I did that?
Yes and yes. The folder is just a bunch of markdown documents, as well as a hidden folder containing configuration, plugins, etc (json, js, css, etc). The vault is entirely self-contained.