Your issue most likely related to this Launchpad Bug #1843507.
The workaround is detailed in the comment #4 on the same thread (which has worked for many):
$ wget http://mirrors.kernel.org/ubuntu/pool/main/libi/libidn2/libidn2-0_2.0.4-1.1build2_amd64.deb
$ sudo dpkg -i libidn2-0_2.0.4-1.1build2_amd64.deb
$ sudo apt-mark hold libidn2-0
Also go through this comment #12, you might need to purge old package.
Edit: To bring the network interface up, go through this post, though I'm posting the solution here, as many people are having this issue today.
If you have an Ethernet cable connect the computer directly to the modem and then:
sudo nano /etc/network/interfaces
Note: Replace "eth0" with actual interface name like "enp0s3". You can find that out with command "ip a".
Append the following lines to the end of the file:
iface eth0 inet dhcp
Ctrl+X to exit and Y to save. Then:
sudo ifdown eth0
sudo ifup eth0
You should get an internet connection. If you do not have a DHCP server use the following instead (if you don't know if you have a DHCP server, then you probably have one so nevermind the following):
iface eth0 inet static
Replacing the address, netmask and gateway values with the ones you are used to.