When you use ssh-add to add an ssh key you get the error: 'Could not open a connection to your authentication agent'. Which means you need to manually start the auth daemon to do any work with private git repos.
I encountered this bug with overwriting my Manjaro Cinnamon installs with Manjaro KDE with 18.1.0 and again with 18.1.2; on two separate machines.
How to reproduce:
Install KDE Edition 18.1.0 and higher.
Use ssh-add, even with no files in .ssh
(When it works it should either complain about not finding a file or add your ssh key.)
A workaround I found is to add an autostart to the user's systemd config:
[Unit] Description=SSH key agent [Service] Type=simple Environment=SSH_AUTH_SOCK=%t/ssh-agent.socket ExecStart=/usr/bin/ssh-agent -D -a $SSH_AUTH_SOCK [Install] WantedBy=default.target
I admit I am new to KDE, but I really believe this is something that should be working out of the box. I use a dotfile manager to configure my machines from a private repo so this is a unique issue I have not encountered on other distros.
The only post I have found related to this was below and no one commented on it.