EDIT:

After reinstalling a few more times (and re-downloading the app), the window stayed up and got stuck at "Cleaning Up..."
I have attached a screenshot of this. Other than the window staying up, everything is the same.

Summary:

The launcher does not launch after the initial update window (see attachment) on Ubuntu 20.04.

Description:

After switching to Linux, I have had some issues installing the Minecraft launcher. When installing (using all methods I've tried, including files from https://www.minecraft.net/en-us/download/alternative) the launcher opens the "Updating" window (see attachments), and the progress bar finishes. After that nothing else pops up (although the process idles at 4% CPU usage). When terminating the process and launching again, no window pops up at all. If the launcher is run from the terminal, a link to a .json pops up (see attachment for more details).

After the first launch, some files are written to /home/(username)/.minecraft, including two logs. All files in the .minecraft, excluding the "launcher" folder and the files within (due to attachment size limits), have been attached. I have also attached the same files after launching the game a second time.

When reinstalling the launcher, I have removed the package, .minecraft folder, and any temp files in /tmp/. I have also tried copying the .minecraft folder from a machine I got it working on, but this did not fix the problem.

Running the launcher in a VM results in the same problem. I have however been able to launch the game on another machine (also running Ubuntu 20.04).

Steps to reproduce:

1. Find yourself a machine running Ubuntu 20.04. I'm not sure what other factors are at play, so I'll stick with this.
2. Download the launcher (I have tested with both normal and alternative downloads, as well as different installation methods)
3. Install and try to launch it.
4. The update-window pops up (see attachments), and the progress bar finishes. If this is the last thing that happens, you have reproduced this successfully.