Is there a command to factory reset Ubuntu?

Try configuring unconfigured packages:

sudo dpkg --configure -a

Update the contents of the repositories

sudo apt-get update

Try to fix missing dependencies:

sudo apt-get -f install

Update all packages with new versions available:

sudo apt-get full-upgrade

Reinstall Ubuntu desktop:

sudo apt-get install --reinstall ubuntu-desktop

Remove unnecessary packages:

sudo apt-get autoremove

Delete downloaded packages already installed:

sudo apt-get clean

Reboot the system to see if the issue was resolved:

sudo reboot

There is no such thing as factory reset in ubuntu. You have to run a live disk/usb drive of any linux distro and backup your data and then reinstall ubuntu.

You can use :

dconf reset -f /

Running this command will reset, among other things: the apps pinned to the Unity launcher or Ubuntu Dock ; panel applets and/or indicators; monitor resolution and interface scaling; keyboard shortcuts; fonts, GTK and icon theme; window button placement, launcher behaviour; and so on.

This command will also reset any application that uses dconf to store its settings. This includes core desktop apps like Rhythmbox, Evince, Shotwell and Nautilus.

This latter point is important to keep in mind as this command may reset library settings, delete accounts, disable plugins, and/or require you to re-authenticate with online services.

On the flip it means this command is the perfect one to run when you want to reset GNOME 3 settings.