That isn’t really the way to fix that issue, the emonhub service unit needs to be corrected to include the log file path in the command as suggested here
it is far better to direct the log messages to the correct place using the correct tool at source than to let them fall into the wrong place (via stdout) and then try and fix after the event with various tweaks and edits. This correction doesn’t seem to have filtered through to the update script as yet, it will of course also need emonhub adding to the list of log folder creation and service restarts in rc.local until a fix to that issue is rolled out too (Grrrr!!!).
Another point re the logrotation is that the wildcard entries have been edited since the logrotation last worked and when logrotation gets fixed again and resumes operation, the /var/log/* will rotate the rotations as if they were separate logs. This is why vague wildcards cannot be used (unless olddir is used and the rotations are not held in the same folder as the logs to be rotated).