I've been dealing with this problem for a couple of months now and I've yet to resolve it.
Almost every hour on the dot, my internet goes out. When I am browsing, I receive on Chrome
DNS_PROBE_FINISHED_NXDOMAIN
if I try to enter any site that is not a Google search or YouTube. By this I mean that YouTube will still load and play videos and I can search things on Google; however, as soon as I attempt to click on any links or enter in a web address that is not one of those two, DNS_PROBE_FINISHED_NXDOMAIN appears. Moreover, if I am on a video on some meeting service (such as Zoom), it too will drop. This also occurs on Firefox with its own version of DNS_PROBE_FINISHED_NXDOMAIN.
This issue occurs on all devices that have Ubuntu 20.04 on them whether or not the device is connected to wifi or to an ethernet cable. On my desktop that is dual booted with Windows 10, it will not occur on the Windows 10 partition. Moreover, the internet does not go out for all devices at once; rather, each individual device has its own timer and when that timer hits the one hour mark, the internet shuts down.
Strangely enough as well, if I go to my network settings when the internet is dropped, it indicates that I am still connected (as also evidenced by still being able to perform Google searches and listen to YouTube, but nothing else).
I have tried a number of things and all have failed. Notably, I have tried adding nameserves to various configuration files (see also and this), restarting the modem/router (of course), sending and arping request, and a couple other less notable/popular suggestions that I've stumbled upon. I've also followed this thread a bit because it seems to be a very similar problem, as does this thread (which seems to have been solved for that user via the first solution that I mentioned).
