Game says "authentication servers are down" due to broken certs on Ubuntu and derivative

Please attach .minecraft/logs/latest.log and .minecraft/launcher_log.txt

There is no indication of such an error in the logfiles.
You've entered suceesfully a game, didn't you?

No i did not.

I can only play single player mode but my skin is set to default slim skin as if the game couldn't load my skin.
When I try to connect to server the message is shown like in the screenshot.

Please attach both logs immediately after having this error.

Those ARE logs after this error. I've specifically deleted all logs prior to generating those two.

I have been doing some fairly extensive digging into this issue, and as far as I can tell it has to do with changes made in Ubuntu and derivatives keystore messing up Java certs (see details here). I have been trying to recreate the issue, but all my testing on a fresh Ubuntu 18.04 box have yielded no results. This leads me to believe that the issue likely only occurs for users who have either multiple versions of Java installed (8 and newer versions), or have had Java since before the change in keystores.

I theorize that the easiest fix would involve uninstalling all versions of java, including dependencies (notably the ca-certificates), then reinstalling openJDK 8 (or equivalent).

I.e., running something like:

sudo apt-get remove <list java versions here>

sudo apt-get autoremove

sudo apt-get install openjdk-8-jre

This is a fresh install of Linux Mint (Ubuntu derivative). openJDK 10 is default/current version for this distro.

Are there any operations you'd like me to perform in order to better diagnose the problem? (other than regressing java version)

@unknown, the current release (and likely many future releases) of the game do not support versions of java newer than Java 8. Furthermore, 8 is an LTS release, so it should be considered safe and stable for quite a while. If you have a need for Java 10, I can understand that. The solution above is a proposed solution; I don't know if that will fix the issue. I am looking for people who are experiencing this to test with the steps I've proposed. If you should try what I suggested, and it does work, you can try reinstalling Java 10 after the fact, and see if that makes a different. Please be sure though that the game is running on a Java 8 jre in that case.

@CubeTheThird, thank you for your help. After reading your comments I've started performing various tests, including changing default version of java for my system with the command bellow. I had 2 versions installed:

~$ sudo update-alternatives --config java

There are 2 choices for the alternative java (providing /usr/bin/java).  Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1101      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1101      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode

 Choosing version 8 didn't solve the issue but... I've noticed that there was an update for "ca-certificates-java" among many others. After installing the update and returning to default version (which is java-11-openjdk-amd64) the issue has resolved itself and I can connect to server as usual. I'm providing the version information of the update fixing the issue below. Please mark this bug appropriately.

Thanks again and have a nice day! 🙂

Wojtek

ca-certificates-java (20180516ubuntu1~18.04.1) bionic; urgency=medium

Thanks for the update. For now it seems updating/reinstalling the ca-certificates-java package may be a viable solution. I will update the ticket accordingly.