I am not using Linux and have had this issue for over 12 hours.
Weirdly, I have installed classic wow on an old laptop & can connect fine, using the same internet connection (I don’t have IPv6 available). I have unstalled wow on main PC & done all the deleting of WTF files etc., but still won’t work.
EDIT: Retail wow won’t connect on main PC either, just for info.
Sane ISP (EE). same problem!
I play on Linux too and can confirm it has stopped working while ingame since yesterday.
My char was heading to Orgrimmar from Thunderbluff while flying when it got unmounted, and started to do odd stuff like teleporting in front of Thunderbluff and falling down without dying, and teleporting back again while system message “Transfer aborted: instance not found” was appearing.
After I restarted it didn’t login back again.
Same problem, not isp-related either, had them check.
Greetings from Finland. ISP’s Elisa (is not working properly) and DNA is working just fine.
On the Elisa fibre connection my MacBook Pro works just fine, but a linux PC get’s the same errors discussed in this thread and gets stuck in server login.
On DNA ISP the Linux client works just fine. VPN doesn’t work on the linux, we tried.
So it’s not all Linux issue, there’s still something else, because it works fine with hotspot on my phone.
I was able to solve this by switching IPv6 support on. BTW i use Arch Linux =P
Enabled IPv6 in both the client and UFW. Reloaded & restarted, but still unable to connect. BTW I use Arch
IPV6 is enabled in Ubuntu by default I think.
Might be, but it’s not enabled by default in the game client. Or everyone with problems and working IPv6 have disabled it manually.
We disabled ipv4 on Ubuntu, enabled ipv6 on WoW Client and still nothing. Anyone guru enough to tell me how to force the ipv6 on?
Same linux problem here, using Telefonica (Spain) ISP.
Just additional info here I,m on retail and windows 10 pc but my phone for the mobile app was on the internet and also my mobile network data when I tried as we turned the internet off last night .
Still the same unable to connect regardless .
The IPv6 has to be selected in the client options under the network tab.
Could it be related to a defence they used against the Ddos which affected all linux user as well?
Well, I would say, it is not linux problem. WoW Companion mobile app isn’t working too… The same problem as on the desktop - cannot connect…
It’s not just a Linux problem, also Mac. Im sure they are doing their best at the moment. Sadly my friends are going forwards and I need to catch them up 
Im on windows and have the same problem…
Any eta???seriously…
That only works if your ISP supports IPv6 to home, which a lot of providers still do not (why I cannot say, Mine included).
Just turned on the IPV6 and still hanging on the logging into game servers then disconnecting.
Like I can understand if it was my internet but I,m having no trouble with anything else infact my nets running smoothly .
More frustrating that there is no update either but mehhh