This message keeps popping up in my journald log after some updates. Don't know if it's worth looking at and fixing, but posting it here for completeness. Thanks!
/lib/systemd/system/plymouth-start.service:15: Unit configured to use KillMode=none. This is unsafe, as it disables systemd's process lifecycle management for the service. Please update your service to use a safer KillMode=, such as 'mixed' or 'control-group'. Support for KillMode=none is deprecated and will eventually be removed.