The Nexus Player does not have a standard PC BIOS. It uses a specialized bootloader. You cannot simply plug in a standard Ubuntu live USB and hit install.
If you want a modern Android TV experience without full desktop Linux, look for unofficial LineageOS builds. While distributed as standard Android .img or .zip files rather than ISOs, custom ROMs bring newer security patches and interface layouts to the aging Fugu hardware. Troubleshooting Common Issues nexus player iso
Before you hunt for an ISO, understand what you are working with: The Nexus Player does not have a standard PC BIOS
Use a tool like Rufus or Etcher to flash the ISO onto a USB drive. Boot and Install: If you want a modern Android TV experience
Extract the contents of the .tgz file directly into your platform-tools folder.
If you need to restore your original ASUS Nexus Player (codenamed ), you should use the official factory images provided by Google.