Install the package for the interfaces. Configure your stuff at /etc/network/interfaces

apt install ifupdown

Start the networking service

ifdown --force enp0s3 lo && ifup -a
systemctl unmask networking
systemctl enable networking
systemctl restart networking

F*ck netplan and systemd networking in the butt

systemctl stop systemd-networkd.socket systemd-networkd networkd-dispatcher systemd-networkd-wait-online
systemctl disable systemd-networkd.socket systemd-networkd networkd-dispatcher systemd-networkd-wait-online
systemctl mask systemd-networkd.socket systemd-networkd networkd-dispatcher systemd-networkd-wait-online
apt-get --assume-yes purge nplan netplan.io

Source: https://tweenpath.net/ubuntu-18-04-disable-netplan-switch-networking-etc-network-interfaces/