Summary: This brings numerous advantages such as:
easier admin configuration with drop-ins, overrides and multiple hooks throughout (and only having to learn one tool)
session cleanup on exit, avoiding that occasional part where shutdown hangs
startup that actually knows when things are up
race free autostart and DBus activation at once
logs that rotate are split by service and usable
resource management through slices and cgroups
Over the past 2 years I've been trying to tidy up and encapsulate the relevant parts of startup into the binary plasma-session so that we can just runtime swap out that one part and supporting both paths will be easy.
Support is toggleable via a configuration option. The default is currently completely off. Then we can change after some feedback.
From Differential Revision: https://phabricator.kde.org/D28305