I can confirm that removing libcurl4-nss-dev and libcurl3-nss resolves the issue.
My guess would be that the reason you could not replicate this problem on a fresh install of the distro is that these packages are probably an artifact of upgrading from a previous version of the distro.
Unfortunately, there are probably many people in this situation. It would be ideal if you could update the launcher to handle the case when these packages are installed.
Marc, thank you for the update.
Unfortunately, I installed the 2.1.7658 version of the launcher from the beta page and the behavior is the same. (I tried both the .deb file and the .tar.gz file.)
Any way to get this issue escalated? It is a show-stopper. It prevents installation of any version of MC. If some version of MC was not already installed using a previous version of the launcher, there is literally no way to play on Linux. Even if there is an existing version of MC installed, there is no way to play online and no way to install a newer version of MC.
That curl command is also runs successfully for me.
I assume that if it were a system problem that it would also have surfaced with the old launcher. This problem only started with the most recent launcher.
The wireshark capture is the same after changing the password. Logging in after password reset does not work for me.
I don't know if this is helpful or not, but I used wireshark to capture network traffic during the period of time that I clicked the "LOG IN" button on the Add account modal on the Accounts setting tab. It appears as though a TCP connection was established to authserver.mojang.com and then immediately closed without sending any data. No other related network traffic was captured.
I can confirm that I see this same behavior.
I was originally logged in from the previous version of the launcher and had the "No connection" message and only the "Play Offline" option. I logged out and now am unable to log back in with the message "Sorry! Make sure you are online and try again", with the "SaveToBuffer failed" message in the console.
Ubuntu 18.04.2 LTS Linux
Kernel: 4.15.0-52-generic
Oracle Java version "1.8.0_181"
Confirmed that version 2.1.7698 from "libcurl-fixed" runs properly when libcurl4-nss-dev and libcurl3-nss are installed. I can log in and play online.
Many thanks for the work on this!