The official stable and beta releases (like PrimeOS 2.1.3) are typically hosted on the PrimeOS SourceForge page.
Use a USB drive with at least 8GB of storage. primeos unoff a11 .iso
The key selling point of this OS is its Desktop Experience. Unlike stock Android, which is designed for touch, the Unofficial A11 ISO is compiled with a "Desktop Mode" priority. The official stable and beta releases (like PrimeOS 2