Huh, I’ve never used chat, I rarely use the friends list, and I think I’ve intentionally used the overlay maybe a handful of times. So I don’t think that’s a big loss.
However, they did work fine on xorg (I haven’t used any of them since switching a few months ago).
Regardless, the launcher works for the primary use cases: buying, organizing, installing, and playing games. So I think that qualifies as supporting Linux, even if there are some bugs here and there.