suspend-then-hibernate works, how to use it by default instead of suspend

I’ve tested the mode suspend-then-hibernate succesfully (sudo systemctl suspend-then-hibernate). I’ve found out how to use it when the lid is closed by editing /etc/systemd/logind.conf. However, that does not work for the power button. So, how can I configure Ubuntu/Gnome to use suspend-then-hibernate by default for the power button and the menu?