update: Was backing up my system to upgrade to Macos Mohave just incase that fixed it, but from the changes shown in Mohave it doesn’t look like theres anything very relevant so I don’t know if I really want to do that upgrade, even though there’s still a small chance it can fix this.
Julien from the github link you sent didnt think it would work as they have said (I’m sure they wouldnt mind me quoting) “I don’t know Joplin but I have seen that it uses node-notifier which is a wrapper around my terminal-notifier tool. I think node-notifier bundles my tool so I’m not sure you can change the version yourself easily.”
So, gamble with a Mohave upgrade, which could mess other things up or struggle with getting this fixed? Any more help always welcome.
Edit: Problem solved, at least solved well enough. Turned my phone ringer back one and went through every other app changing its settings. So just joplin can ding my phone and everything else is chilled and relaxed. It still doesn’t give the desktop notification but this will do, so the technical issue isn’t resolved at all, but this workaround will do.