It seems like you misunderstand what Joplin is? Or I misunderstand what you are saying… I don’t know…
Joplin is a note taking app that fully works on markdown. You can use it on your local PC, but you can also synchronize the notes over devices.
Joplin is hosting the image on the user’s instance - you’re in feddit.de, so it uploads to feddit.de.
Joplin and Lemmy have nothing to do with each other. I have just taken a screenshot of the rendered markdown document in my Joplin app, switched to my web browser, opened feddit.de and posted the screenshot in this community.
If you want to say that using Joplin just to draw and post pictures somewhere, would be a bad idea… Yes, that’s right. But it’s primarily a note-taking app, so that’d be expected… And usually, the notes are private and nothing you want to regularly post online…
Meanwhile, the old reddit app I used to use (Relay) would upload to imgur, all seemlessly in the background, then paste the link code in my comment. This kind of functionality is what I would like to see.
I’m generally against hosting files on instances, anyway. It creates extra server load.
Well, Lemmy is a decentralized system. Hosting all image resources on a centralized service (imgur) is probably not what the majority wants…