If for any reason you want to undo the existing configurations in the equipment, you can restore the factory configuration (Factory reset).
You may want to do this procedure for example if the equipment has been misconfigured in such a way that the devices is not accessible any more, or because you want to start the configuration from scratch to add the equipment in another network, or simply because you are exploring the possibilities and want to return to the beginning 
Factory reset of a LibreRouter
To do this, you have to turn on the equipment and wait at least one minute for it to start. After this, the unit’s reset button must be pressed for 10 seconds and then released. Then you must wait at least 5 minutes and you should be able to see the same already in the original factory settings.
Here is more information about this procedure: (https://openwrt.org/docs/guide-user/troubleshooting/failsafe_and_factory_reset#factory_reset)
In general this method always works although there are a few cases where it does not. In these cases the following method can be used
Failsafe mode of a LibreRouter
This mode is used to access or modify the router configuration without doing a factory reset. It can also help when the factory restore mode does not work.
To enter this mode, what you have to do is restart the equipment (connect the equipment to power) and intermittently press the reset button (that is, press and release, press and release, press and release) for 25 seconds. After that time the device enters failsafe mode.
In this mode, the device has the IP address 192.168.1.1 and only works through ethernet. It does not have DHCP so it is necessary to configure the computer in an IP address such as 192.168.1.2 and then enter via SSH with root user (root@192.168.1.1).
Once inside you can run the firstboot command to do a factory reset of the computer. You can also run the mount_root command to mount the configuration partition and modify files if necessary.
You can read more about this process here: https://openwrt.org/docs/guide-user/troubleshooting/failsafe_and_factory_reset#failsafe_mode