Having had a working Ubuntu Mate desktop for over a decade, dutifully updating and upgrading along the way (now on Jammy and Mate 1.26.0) I have had few problems.

Then 3 days ago, no internet.
I was even complaining to Vodafone (through the Vodafone fibre, with a telephone connected to the Vodafone router - wasn't thinking, just panicking).

Firefox, Chrome, Brave and Thunderbird mail all "No server" EXCEPT I could browse anything in my LAN, including the router and my NAS.

Trawling through the forums on a 20 year old laptop with fading screen, I found that "eth0" could disappear and be replaced by some weird label, in my case "enp63s0".

As advised on a forum, I changed /etc/network/interfaces to suit.
Shouldn't have bothered.

I then found somewhere else that I should alter /etc/default/grub and update/reboot.
Hey presto, I got eth0 back.
But no internet..

Out of desperation, I tried Telegram.
Lo and behold, it worked.

So I then tried my VPN, fired up my browser and everything came up as though nothing was wrong. Without the VPN it's back to "No server".

What's going on?

Can I just find my DVD and reload my network interface thingy, or is there another way?

enp63s0 is not weird but self-explanatory, modern udev constructs network interface names this way, leave it alone because it matters not a jot how it is called. The useful bit of information here is that telegram works while nothing else does. Unlike the vast majority of programs, telegram connects to its servers by ip addresses, not by symbolic names, so it indicates some sort of DNS misconfiguration. Further reading: https://www.google.co.uk/search?q=tr...ting+dns+linux

If it's DNS related, pinging a domain name will fail but pinging an IP address will work - e.g. compare "ping -c4 example.com" and "ping -c4 93.184.215.14"

Check whether you have DNS configured in /etc/resolv.conf (Also, because you're on a systemd-based distro, there's a bunch of complexity added which systemd-resolved may or not explain.)

Check the contents of /etc/nsswitch.conf - what does the hosts line contain?

Check the router? Maybe it's had an update and/or restart which reset some settings?

Hi all and thanks for getting back.

Yes the IP addresses works and the names didn't.

I don't know why I did, but I tried the VPN, and everything came up on the browser.
I then switched off the VPN and everything still worked.

I even rebooted. So far, everything is good.

Still a tad confused, but hey ho!