Summary
My iMac having Ubuntu kept having high CPU usage with the program sddm-greeter.
Solution
Amending the file /etc/security/pam_env.conf fixed up the issue :
/etc/security/pam_env.conf
======
#
# Avoid high cpu usage with sddm-greeter
# https://github.com/sddm/sddm/issues/323
QT_QUICK_BACKEND DEFAULT=software
Top comments (1)
This is a very poor, nonspecific, whole-system reduction-in-functionality solution. It boils down to completely giving up on hardware accelaration in many important contexts. My KDE desktop looks different after enabling this workaround (e.g. desktop icon labels get background rectangles instead of being text-shaded) because a lot of code paths in KDE Plasma choose different, less CPU-intensive visual effects when software rendering is forced.