I upgraded my Ubuntu release from 16.04 to 18.04 using sudo do-release-upgrade and following the instructions; the system boots correctly to the login page, but when I click on my user name, it says automatically (I do not enter any password) "Autentication error". Then the screen goes black in just a second and a message "Failed to start Load Kernel Modules" appears, along with many other lines:

So I restarted in recovery mode, used the root shell to run sudo systemctl status systemd-modules-load.service, and that's the result:

As suggested in many other topics (for example: What to do after Failed to start Load Kernel Modules), I tried to enter
apt-get update
apt-get dist-upgrade
apt-get -f install
but I get the message Could not resolve 'archive.ubuntu.com' (i.e., there is no internet connection), while for
dpkg --configure -a
I get dpkg: error: unable to access dpkg status area: Read-only file system.
Running ifconfig I see this result:

so I cannot connect to any network.
I could appreciate any help in resolving this (I'm not an expert in Ubuntu)
EDIT:
Result from ifconfig -a:
