Download Solaris 11.4.42 CBE ISO
https://www.oracle.com/solaris/solaris11/downloads/solaris-downloads.html
Upload to Proxmox local ISO images
[1] Create VM
[2] Choose downloaded ISO
[3] Guest OS: Linux 5.x (PVE 6,7.x) or Solaris Kernel(PVE 8.x)
Specs