Same DE, Gnome shell. Standard Ubuntu comes with 2 system extensions; Ubuntu Dock and KStatusNotifierItem. The non-standard is Gnome-shell with whatever extensions you need without those 2 system extensions.
Sometime ago Ubuntu had its own DE, something exclusive, but now it has a DE that anyone can have with any base, Arch, or Debian or whatever. The extensions are also for any distro with Gnome shell. Even those 2 Ubuntu system extensions can be installed in any other Gnome distro, even though they are not available at extensions.gome.org, just copy and paste.