Updating server OS, installation and internet connectivity issues in using Ubuntu Server

Question

I recently installed the latest version of Ubuntu using the alternative downloads page as I didn't have network connectivity during the installation process. After a successful install, when I try to run some basic commands, I get "ubuntu server says package is not available but is referred to by another package. This may mean that the package is missing, has been obsoleted". I did some research online to find out that the most likely solution to this is to update my apt repo, however without internet connection I have not been able to run sudo apt-get update successfully.

I have wireless internet available, but Ubuntu hasn't even been able to detect my interface. Ubuntu is the only OS I have in the machine. From the information I have gotten online, the commands that I need to get my interface working return the same error, "ubuntu server says package is not available but is referred to by another package. This may mean that the package is missing, has been obsoleted", and since I can't update I don't know how to go forward from here. I don't have access to any ethernet connection.

Please I need recommendations on other options to gain access to the internet.

lspci -nnk | grep 0200 -A3 returned:

00:if .6 Ethernet controller [0200]: Intel Corporation Ethernet Connection 1219-LM [8086:156f] (rev 21)
Subsystem: Hwelett Packard Company Ethernet Connection 1219-LM [103c:8079]
Kernel driver in use: e1000e
Kernel modules: e1000e

cat /etc/netplan/*.yaml returned

version: 2
renderer: networkd
ethernets:
enp0s31f6
addresses: [127.0.0.1/24]
nameservers:
search: [myname-server]
addresses:

ip addr show returned

1: lo:  mtu 655536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/B scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s31f6:  mtu 1500 qdisc noop state DOWN group default qlwn 1000
link/ether ec:8e:b5:a2:6e:55 brd ff:ff:ff:ff:ff:ff
3: wlp2s0  mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether b8:8a:60:50:40:c4 brd ff:ff:ff:ff:ff:ff

Answer 1

Your netplan file specifies an address that belongs to the loopback interface; it's already in use. You failed to specify a gateway or DNS nameservers,

I suggest that you amend the netplan yaml file to something like:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s31f6:
      addresses:
        - 192.168.10.102/24
      gateway4: 192.168.10.1
      nameservers:
          search: [mydomain,otherdomain]
          addresses: [192.168.10.1, 8.8.8.8]

Of course, susbstitute the details matching the network to which you are connected. Spacing and indentation are crucial and must be perfect; proofread carefully twice.Follow with:

sudo netplan generate
sudo netplan apply

After a reboot, your ethernet should be connected.