GNOME alternatives / equivalent for Klipper?

You have:

Glipper - Klipper's Brother... for GTK. It has a limited amount of entries (MAX 99 Vs Klipper with 1024) but has nice features like sync different Glippers in the network, smart detection for similar clipboard copies and others. After a couple of versions ago, Glipper is GONE!. What you can do in Ubuntu 18.04+ is install the Gnome Extension Clipboard Indicator here https://extensions.gnome.org/extension/779/clipboard-indicator/

Parcellite - Small clipboard manager. Very nice and simple.

Synergy - You can share clipboard over Network (Including Mouse and Keyboard)

xfce4-clipman / xfce4-clipman-plugin - Klipper's Smaller Brother.. for xfce.

Install by:

sudo apt-get install glipper

sudo apt-get install parcellite

sudo apt-get install synergy

sudo apt-get install xfce4-clipman

Try Clipit

Install via Terminal:

sudo apt-get update && sudo apt-get install clipit

Diodon

Install by using the PPA via Terminal:

sudo apt-add-repository ppa:diodon-team/stable
sudo apt-get update
sudo apt-get install diodon diodon-plugins