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

Reference

• high cpu when sddm-greeter is idle

Related Post

• Enable your Linux Machine to show login (SDDM) with Aerial Theme when motion is detected