In the last couple of weeks, I replaced Windows 10 on my main desktop machine with Lubuntu 18.04, as I had long grown tired of forced Windows 10 updates with lengthy processing that tended to fail anyway.
The desktop in question is using a Wifi dongle to access the internet, as a wired connection would be very awkward for where my computer is located. Connection to the Wifi network itself is consistently successful. Often, as per now, I am able to browse the internet, use the Software Updater, etc. But, I can come to the computer say a couple of days later, and although Wifi is connected, trying to go to sites in Firefox gives an 'Unable to connect' error page.
Once the connectivity is in the 'broken' state, I find that
sudo service network-manager restart does not sort it, nor do repeated reboots. In such situations, I still have Windows 10 on a laptop and can go on there to perform whatever task requires online access. However, I would very much prefer to keep use of Windows 10 to a minimum if I could.
I can then come back to the the desktop Lubuntu machine say a couple of days later, and sometimes it might still not be able to browse sites; but at some point it 'fixes itself' without me having done anything.
The laptop I mentioned is dual-boot Windows 10/Ubuntu, and when using Ubuntu 17.10, I would have a similar experience. I could go on some days and be able to browse; then on another day, browsing would not be working; then at some point it would 'fix itself'; and then at a later date, browsing would again not be working; then it would fix itself; and this cycle seems to repeat.
Before I replaced Windows 10 on the desktop, it was dual-boot Windows 10 and Linux Mint. I had the same intermittent connectivity problems with Mint.
So it seems to me that out-of-the-box Ubuntu family distros can be prone to this intermittent inability to browse - and have been for a considerable time??
Does anyone know of any diagnostics that can be tried while the affected machine is working fine? Or, is it necessary to wait for the problem to occur, and only then are the diagnostics useful?
TLDR: Wifi on Ubuntu family distros consistently connects, but on some days I can browse and on others I can't; then another day it's 'fixed itself'; and this cycle seems to repeat.