Thanks! On systemd-based systems:

    in /etc/systemd/logind.conf:                                       
        HandleLidSwitch=ignore
        HandleLidSwitchExternalPower=ignore
        HandleLidSwitchDocked=ignore

Then:

    systemctl restart systemd-logind

In addition, some desktop environments may also trigger suspend. If so, there should be options in the power settings menu.