ObsidianOS is described as 'Arch-based Linux distro with an A/B partition style so if a package has a breaking change that causes some issues, you can just reboot into the other partition and restore the other one, while relying on the robustness of EXT4' and is a Linux Distro in the os & utilities category. There are more than 50 alternatives to ObsidianOS for a variety of platforms, including Linux, Self-Hosted, BSD, KDE Plasma and Fedora apps. The best ObsidianOS alternative is Linux Mint, which is both free and Open Source. Other great apps like ObsidianOS are Ubuntu, Debian, Fedora and Arch Linux.