The lab also adds a second network for task 2, so your own connection to the VM is never touched: interface le-lan, with a machine at 10.98.0.1 on the far side. On the RHEL family it has the NetworkManager profile lab-net, which gets an address by DHCP from that machine. Ubuntu Server uses netplan with networkd and doesn't install NetworkManager, so there le-lan starts with no address, and you do tasks 1 and 2 with netplan.

Tasks

Find the configuration file of the main interface, and write its path to /root/lab-answers/1. RHEL family: read nmcli device and nmcli connection show, find the file of the active connection with nmcli -f NAME,FILENAME connection show, and read it with sudo. Ubuntu: read the files in /etc/netplan/ and networkctl status, and find the netplan file that sets up the main interface.
Give le-lan the static address 10.98.0.10/24, check with ip addr and ip route, and reboot to show it lasts. RHEL family: on profile lab-net, with nmcli connection modify, then bring the connection up. (The chapter then returns it to DHCP: do that after you've run the check.) Ubuntu: in a new netplan file, /etc/netplan/90-lab.yaml, applied with netplan try.
Change the host name to lab2.example.net with hostnamectl, and check /etc/hostname, the prompt in a new shell, and hostname -f.
Add the name files.lab.example for the peer's address, 10.99.0.2, to /etc/hosts, and ping it by name.

Hints

nmcli -f NAME,DEVICE,FILENAME connection show --active. On Ubuntu, ls /etc/netplan, networkctl list, networkctl status.
nmcli connection modify lab-net ipv4.method manual ipv4.addresses ..., then nmcli connection up lab-net; ip -br addr show le-lan.
In netplan, an ethernets: entry for le-lan with addresses: [10.98.0.10/24]; chmod 600 the file; netplan try (press Enter to keep it).
hostnamectl set-hostname, hostnamectl status.
One line in /etc/hosts: the address, then the names; getent hosts.