Going to https://vanillaos.org/ https://vanillaos.org/ and scrolling down, I encounter a section with the title "Immutable.." which seems to be what you're look

Going to https://vanillaos.org/ https://vanillaos.org/ and scrolling down, I encounter a section with the title "Immutable.." which seems to be what you're looking for? > ..but also not. > Vanilla OS is an immutable operating system, core parts of the system are locked down to prevent unwanted changes and corruption from third-party applications or a faulty update. Some paths are still writable, such as the home and configurations directories, this allows the user to keep their files and ensure the normal functioning of applications. > Core components are only updated via controlled and atomic transactions, which are applied only on success and made available on reboot. > Need to install a component in the core system? No problem, you can open a transactional shell at any time, make your changes and let the system apply them automatically!