Testing whether hibernation is possible can be done by running systemctl hibernate as root. If the command does not work, there are ways to investigate the matter detailed in the friendly post at: https://fostips.com/enable-hibernate-linux-mint
For a system that has swap and the other configuration enabled but lacking a visible Hibernate command in the Power menu, a file can be created at /etc/polkit-1/rules.d/10-enable-hibernate.rules with the following content:
polkit.addRule(function(action, subject) {
if (action.id == "org.freedesktop.login1.hibernate" ||
action.id == "org.freedesktop.login1.hibernate-multiple-sessions" ||
action.id == "org.freedesktop.upower.hibernate" ||
action.id == "org.freedesktop.login1.handle-hibernate-key" ||
action.id == "org.freedesktop.login1.hibernate-ignore-inhibit")
{
return polkit.Result.YES;
}
});
And that’s it.