These are the highlights of the new version 5.4:

  • Debian Stretch 9.8 and Linux Kernel 4.15,
  • New installation wizard for Ceph,
  • New HA policies freeze/fail-over/default for greater flexibility,
  • Suspend to disk/Hibernation support for Qemu guests,
  • Support for Universal 2nd Factor (U2F) authentication,
  • Improved ISO installation wizard,
  • New options for Qemu guest creation wizard,
  • and many more..

More complete details see Proxmox VE Website