When I add an image from the voyager app on lemmy.zip or piefed.zip that’s how it seems to be done - the image is uploaded to the pictrs server and then hyperlinked exactly like that. Piefed.zip is down right now so I can’t test if it’s the pictrs upload (suspect this one) or the hyperlinking, but I’ll play with it more later to find out. Thanks!
Anywhere public. So you could create a dummy post to get your picture to your instance (or whatever other method) and link it like this:

Note the reclamation before the brackets. That’s what tells clients to embed the picture.
When I add an image from the voyager app on lemmy.zip or piefed.zip that’s how it seems to be done - the image is uploaded to the pictrs server and then hyperlinked exactly like that. Piefed.zip is down right now so I can’t test if it’s the pictrs upload (suspect this one) or the hyperlinking, but I’ll play with it more later to find out. Thanks!
Anytime! And good luck.