Desktop Environment Showcase

For reference:

• What is a desktop environment?

For window managers, see Window Manager Showcase
For stylized screenshots, see Rice Showcase

For OS specific changes to desktop environments, OS Specific Adjustments

Popular Desktop Environments

Unity (Personal Favorite)

GNOME (v 44)

KDE Plasma 5

Cinnamon

MATE (GNOME 2 Fork (means derivative))

Pantheon

Budgie

Enlightenment

Lightweight

Xfce

LXQt (LXDE)

Less popular

Deepin (20+)

Deepin (15.11, personal favorite)

Cutefish

OS Specific Adjustments

Manjaro GNOME Edition

Manjaro GNOME edition allows changing GNOME layout. This screenshot was prior to GNOME 40, but I think they should still have it.

Zorin OS

Zorin OS is an aesthetically themed OS based on Ubuntu GNOME. It also supports multiple layouts

Ubuntu MATE

Ubuntu MATE also allows changing layouts

Ubuntu

Ubuntu adds a number of extensions on to stock GNOME to brand it.
I have listed a few differences between Fedora's stock GNOME and Ubuntu here: Converting Fedora to Ubuntu

Pop OS

Pop OS is migrating from GNOME to their own COSMIC desktop environment. A major distinciton from Ubuntu's appearance is the use of a tiling window extension named Pop Shell.

I listed some of the differences here: Converting Ubuntu to Pop OS