At least once one open-source OS supports a bit of hardware, the other ones can look in and see what they need to do. That doesn't prevent them from lacking the

At least once one open-source OS supports a bit of hardware, the other ones can look in and see what they need to do. That doesn't prevent them from lacking the personpower to actually do it, but it drops the effort required to reverse engineer from scratch dramatically, if someone becomes interested enough.