How to prevent systemd from killing a process that belongs to an idle session

Issue

• User specifies a value for StopIdleSessionSec in the /etc/systemd/logind.conf configuration file (e.g. due to a STIG requirement).
• All processes started by a user during a session get killed when the inactivity timeout is reached.
• Using nohup to start a process does not solve the problem.
• Processes are killed even when having KillUserProcesses=no in the configuration file.