Please read this thoroughly. While there have been similar issues in the past, I have ruled out all the answers for them. I've already contacted support, and they were unable to resolve the issue.

I will list the technical details and attempted fixes exhaustively below. Again, please review this thoroughly before closing. Even if it is a duplicate (although I already searched for duplicates), the technical detail below may make this useful.

I am on an up-to-date Ubuntu computer, and I'm trying to connect to public Minecraft servers (I don't host or control them). Exact system and game version numbers are above. I am willing to send the exact versions of anything else related.

Every time I try to connect to any Multiplayer server, I get the following error message:

Failed to connect to the server. Failed to log in: The authentication servers are currently down for maintenance.

I have already followed your Troubleshooting guide and multiple other references online, and have ruled out all of the following:

• I have logged out of my Minecraft account on the launcher, and logged back in (three times).
• I have uninstalled and reinstalled from the .deb (twice), completely removing the ".minecraft" folder both times.
• I have updated my computer, including graphics drivers.
• I have restarted my computer.
• I have confirmed my firewall is disabled; it was disabled before the last install of Minecraft. I have no antivirus software on the system.
• I have confirmed no software is running on my system which could block a connection.
• I have confirmed that your authentication servers are currently up (via status on help.mojang.com).
• I have confirmed the problem on both wireless and wired (ethernet) connections to the router.
• I have restarted my router.
• I have confirmed that I can connect to 'authserver.mojang.com' via my web browser on this machine.
• I have confirmed no packet loss on connection to 'authserver.mojang.com' via the terminal command

  ping -c 100 authserver.mojang.com

  Results: 100 packets transmitted, 100 received, 0% packet loss, time 99133ms, rtt min/avg/max/mdev = 17.092/48.364/230.986/31.455 ms

• I have confirmed that I can connect to the server on another Ubuntu 18.04.1 computer on the same internet connection. (It runs the old launcher, see note below).
• I have confirmed that others are NOT having problems connecting to the server on different machines and networks.
• I have tried to connect to another server, which currently has several dozen active players, and had the same error.
• I have not had problems running Minecraft on this computer before 27 July 2018. As of 25 July 2018, I COULD connect from the old launcher on this machine, installed via Snapcraft. That updated today automatically, and I had the above problem. I uninstalled and reinstalled the Snapcraft version, before uninstalling it and installing from the .deb on your website.
• This problem persists even now (09 August 2018).

I am a professional IT and programmer with extensive Linux and debugging experience. I am available to perform any tests necessary on the affected machine, even highly technical ones.