Apparently this isn’t standard anymore, and I can see how developers don’t like it, but an antitrust lawsuit over this just seems poorly justified. For whoever doesn’t want to sell on Steam under their conditions, there is Epic, GOG, Humble and ItchIO. Maybe those don’t sell as well, but that’s the choice the company is making.

I don’t think being the largest store by itself is grounds for this sort of legal action. Especially not when they became the biggest store simply by providing good services for a good price, rather than any sort of restrictions at companies publishing in it.