An extended version of this GNOME shell extension is maintained by Deminder (https://github.com/Deminder/ShutdownTimer). You can install it from https://extensions.gnome.org/extension/4372/shutdowntimer/.
Shutdown/suspend your device after a specific time. This extension adds a submenu to the status area.
There is a settings menu where you can change the following:
- Maximum timer value
 - Default slider position
 - Show settings button in widget
 - Root mode: Uses "pkexec shutdown" command instead of default GNOME shutdown dialog. If monitor turns off while shutdown timer is running, then default timer in rootless mode gets interrupted. With root mode activated this can not happen, but you have to enter the root password.
 - Suspend mode: Suspend device instead of shutdown
 
Visit https://extensions.gnome.org/extension/792/shutdowntimer/ and follow the browser extension install instructions.
Build, extract and copy ShutdownTimer@neumann directory to ~/.local/share/gnome-shell/extensions
$ gnome-extensions pack --podir=po --extra-source=timer.js --force src
$ unzip -o -d ShutdownTimer@neumann [email protected]
$ cp -r ShutdownTimer@neumann ~/.local/share/gnome-shell/extensions
$ rm -rf ShutdownTimer@neumann/
$ rm [email protected]
Install gnome-shell-extensions
$ sudo apt install gnome-shell-extensions
Open GNOME tweak tool and enable Shutdowntimer in extensions menu.
$ gnome-tweaks
If gnome-shell-extensions were already installed and you want to refresh GNOME shell after manual installation, do
$ killall -SIGQUIT gnome-shell
Install org.gnome.Extensions via flatpak
$ flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
$ flatpak install flathub org.gnome.Extensions
Open GNOME shell extension tool
$ flatpak run org.gnome.Extensions
Press ALT+F2, type r and press Enter
$ killall -SIGQUIT gnome-shell
- Press 
ALT+F2, typelgand pressEnter - Run 
journalctl -fin terminal 
You can use POEdit or Gtranslator to create or update a translation file (.po) based on the src/po/ShutdownTimer.pot template.
Use gnome-extensions tool
$ gnome-extensions pack --podir=po --extra-source=timer.js --force src
