Ubuntu Core is described as ', a minimalist rendition of Ubuntu , is a lightweight, transactionally updated operating system designed for deployments on embedded and IoT devices, cloud and more' and is a Operating System in the OS & Utilities category. There are more than 100 alternatives to Ubuntu Core for a variety of platforms, including Linux, Self-Hosted solutions, BSD, Windows and Mac. The best alternative is Debian, which is both free and Open Source. Other great apps like Ubuntu Core are Linux Mint (Free, Open Source), Manjaro Linux (Free, Open Source), Fedora (Free, Open Source) and Windows 10 (Paid).
MINIX is a POSIX-compliant Unix-like operating system based on a tiny microkernel running in kernel mode with the rest of the operating system running as a number of isolated, protected, processes in user mode.
antiX is a fast, lightweight and easy-to-install linux live CD distribution based on MEPIS and Debian's testing branch for Intel/AMD x86-compatible systems. antiX offers users the "Magic of MEPIS" in an environment suitable for old computers.
BunsenLabs Linux is a distribution offering a light-weight and easily customizable Openbox desktop. The current release is Helium, built on top of Debian (stable). The project is a community continuation of CrunchBang Linux.