Basically every Ubuntu upgrade I run into this issue of my network connection dropping all the time – at least it looks that way. What temporarily solves it is clicking the “Auto Ethernet” item in the Network menu, but when it happens once every few minutes, it gets pretty frustrating. Especially since plenty of JavaScript based sites don’t handle sudden errors like that properly so I often ended up clicking on the retweet button a bunch of times before I realized something was wrong and confirmed it was my connection (again) in the browser’s console.
It kept throwing errors like DNS_PROBE_FINISHED_BAD_CONFIG and various other DNS related errors (NXDOMAIN, NO_INTERNET). Searching the net gives plenty of options for possible points of failure, and fixing the NetworkManager.conf (that was overwritten during the upgrade) helped me before.