JetBrains Daemon isn't running: exit code 101 (DE_ELEVATION_FAILURE) on Linux as root

Problem

On Linux, the JetBrains Daemon does not start. The Toolbox App log under ~/.local/share/JetBrains/Toolbox/logs shows this for every launch attempt:

[DaemonClient] bundled (attempt 1): ".../jetbrainsd/bin/jetbrainsd" exit with 101 (DE_ELEVATION_FAILURE)
Failed to launch the daemon on consecutive attempt 10.

The daemon output in the same log ends with:

Refusing to run with the current privileges outside of a container
De-elevation not possible: SUDO_USER is not set

Cause

The Toolbox App runs as root, for example, in a desktop session of the root user. By design, jetbrainsd does not run as root outside a Docker container. It can drop root privileges only when it is started through sudo, and a root login has no `sudo` context.

Resolution

1. Quit the Toolbox App.
2. If the machine has no regular user account, create one as root:
useradd -m user
passwd user
3. Log in to the system as that user.
4. Download and start the Toolbox App again from that account.