This is what drives me nuts with so many of these EU antitrust articles lately.
They're clear about the fine, but then it's all handwavy language about what a concrete violation even looks like. So it's impossible to even have an opinion because nobody even knows what we're actually talking about.
Best I could gather from the article is that this has something to do with paid ads on Facebook and Instagram that link to Marketplace vs. paid ads that link to other similar services (like eBay I'm guessing?), and that there's something extra-special about the Marketplace ads that the eBay ads don't have. But what even is the special thing? And is the article even accurate on this? Because it also refers to Marketplace listings as "ads" so it's not easy to parse.