I'm following Joy of Tech comic via RSS in Miniflux but the image was never loading.
I found half a solution on this blog post of Jan-Lukas Else, unfortunately the proposed solution fails probably as a consequence of some changes in the format of Joy of Tech pages.
The fix is quite simple actually. Edit the feed settings, set the scraper rules to the following:
p.Maintext > img[src$=".png"]
And of course enable "Fetch original content" in the feed options.
And voilà, simple and beautiful.