Desktops such as GNOME have moved processes from the per-session scope, into the per-user systemd manager (
systemd --user). This includes GUI apps such as GNOME Terminal.
What does GNOME use the systemd user manager to achieve? Is there a rationale somewhere I can read?
GNOME appears to copy the environment variables of the session into the user manager. Note that GNOME does not support the user logging in more than once at the same time. These environment variables include, intentionally or not, XDG_SESSION_ID.
loginctl, as in
loginctl lock-session, ended up being modified to support this second, less well-defined concept of a session.
I'm curious what prompted people to create this strangeness.