You can download from this page pre-configured Linux image for single board computers.
CORE2-ROS image - Linux + ROS image for single board computers
Customized Linux operating system for Rapsberry Pi 3/4, ASUS Tinker Board and UpBoard with pre-installed ROS packets, Husarnet, and software to communicate with CORE2 real-time control board.
Ubuntu 18.04 + ROS Melodic - suggested for creating new projects