In power settings, suspend is disabled. However, the PC still goes into a suspend state after approximately 30 minutes. This behavior does not happen under Ubuntu Budgie on another SSD in the same PC. This is a desktop, not a laptop. Is the behavior intended, or is there a way to disable this that I'm not finding?
This is a known bug: https://github.com/elementary/switchboard-plug-power/issues/89
There's a workaround near the (current) bottom of the page:
This problem is because the power settings are used from the gconf configuration of the user lightdm, and not the current user. Just test:
sudo su su - -s /bin/bash lightdm gsettings get org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type
If you change the settings of the user lightdm, the problem disappears
A little further down, it says you need to set the key to "nothing" (still as the lightdm user):
dbus-launch gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type nothing
You might get a message
No protocol specified, which you can ignore.
I had the same issue. I had set "Suspend when inactive" to "Never", but it would still suspend when idle.
Because I don't care to EVER put this system into suspend mode (automatically or otherwise), I also did another couple of things:
I set the power button action to "do nothing".
And I did this command from the Debian wiki, to completely disable any suspend actions:
sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target
Now it doesn't suspend itself. I suspect that the systemctl command was the specific thing that did the trick, but I haven't done any further tests to see whether the power button setting also helped.