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