Systemd 230 was released just last week and it has taken heat not only for opening up FBDEV to potential security issues, which already reverted, but also for changing the default behavior of user processes.

Systemd 230 made a change where KillUserProcess defaults to yes. This terminates user processes that are part of the user session scope when the user logs out. This is causing problems for ssh-agent, screen, and other common Linux processes.

If you would like some weekend reading, there's a lengthy Fedora devel thread about this issue. Additionally, there's a Debian bug report about the problem of systemd now killing background processes after a user logs out.

This new functionality can be disabled by editing your systemd configuration and disabling KillUserProcess.