BakiDance

Since I've first responded to this ticket I have rebuilt my PC and installed a different distro. I'm now using Pop!_OS 20.04 (GNOME), rather than Ubuntu 18.04, and this bug is still present. I've used KDE on this same machine and this bug does not happen on that desktop environment. At no point is FPS a factor in when this happens. My game has never been lagging when this happens; and it nearly always happens when opening the chat or entering a command.

This seems to be directly related to GNOME (perhaps on Ubuntu-like systems?), and happens regardless of system load or game lag.

This seems to only occur on GNOME DE (after versions 3.36.x?). Still, this bug does not occur on versions before 1.12.

As @@unknown discovered, a BIOS update fixes the issue. If you find yourself in this position (assuming you're using a Ryzen 3XXX chip), check to see if your CPU is affected by the RDRAND bug. There's more info on that here (including a script to test it). If your CPU is affected, a BIOS update should fix it, but you're on your own for that. I had to reinstall the minecraft-launcher package after booting back into Ubuntu, but at least it's working again.

I'm also getting this issue on Ubuntu 20.04. Running Ryzen 5 3600 and NVIDIA RTX 2070 Super. launcher-log.txt displays:

Constructing launcher controller with workDir: .../.minecraft, isActive: 1

CPU usage jumps to 100% as others described, but no window opens. Also, as OP stated, this only started happening after I updated the launcher to the latest version. Previous versions worked fine (sadly I don't have version numbers or a backup of the older .deb).

Can confirm for Ubuntu 18.10.This issue is not present in older versions.

Binding the input key for chat/command to one that does not typically insert a text character is a work-around. (For example, setting "open chat/command" as Enter negates the duplicate t or /).