Hi after last upgrade of webmin ad virtualin this message “Unable to open /etc/network/interfaces” appear when virtual min is loaded and i can’t view summary reports like some days ago.
# ifupdown has been replaced by netplan(5) on this system. See
# /etc/netplan for current configuration.
# To re-enable ifupdown on this system, you can run:
# sudo apt install ifupdown
Create a file /etc/network/interfaces with the above content, owned by root with 0644 permission. This is what I see on my Virtualmin on Ubuntu 18.04.