Available OS images:

Main distros:

DISTRO    VERSIONS
Alpine    3.23
Debian    13
Fedora    44
Rocky     10
Ubuntu    26.04, 24.04

Experimental distros:

DISTRO      VERSIONS
Arch Linux  current
NixOS       25.11

Ubuntu 26.04 is the default Ubuntu image.
The SSH CLI also accepts full active image names.