Ok, that wasn’t my hunch! That’s the error I was getting when I used StandardOutput=file: and that was caused by the “file:” specifier only being available from systemd v236.
Interestingly, the error says type but your post has Type - are you sure the service file is in Sentence case as you posted it?
FWIW, the version release history of systemd can be found here: systemd/NEWS at main · systemd/systemd · GitHub