The article is about Boomer Shooters that are fully verified on Steam OS. I can’t find anything that indicates this is even available on Steam, much less fully verified.
Right now I can’t test it. So all I can do is say “not fully verified for steam deck,” which is what my post was about. If you would like, post a list of open-source boomer shooters that are cross platform. I bet people would be interested in the list.