Hey, everyone. I was also looking for something to use with Safari. I managed to build a working version of a Safari App Extension for Joplin. Now that Apple announced future versions of Safari will support Web Extensions, this might only be useful for a little while, this should work for at least a few months. Tested on Mojave and Catalina. Beta code but usable for daily use.
See this post for more info: https://discourse.joplinapp.org/t/safari-app-extension-for-joplin-now-available/9660
Or this for a download: https://github.com/cweirup/JoplinSafariWebClipper/releases/download/v0.1.2/Joplin.Clipper.zip
Hope that helps!