dhclient
is the Dynamic Host Configuration Protocol (DHCP) Client one would use to allow a client to connect to a DHCP server.
$ sudo nano /etc/rc.local
#!/bin/bash
dhclient
exit 0
$ sudo chmod 755 /etc/rc.local
$ sudo systemctl enable rc-local
$ sudo systemctl restart rc-local
$ sudo systemctl status rc-local
Thank you for helping me solve my issue: Ubuntu 18.04.4 LTS connected to home router, but not connecting to the internet unless 'sudo dhclient' is run after bootup.