Well, for Blackmagic products you usually need to attach hardware that is well beyond most home budgets. What distributions they do or do not support is immater

Well, for Blackmagic products you usually need to attach hardware that is well beyond most home budgets. What distributions they do or do not support is immaterial for the linux desktop, but they were provided as an example of their approach. For GoG, they run very well everywhere; they just explicitly support Ubuntu. The point was, that WMs are not even a factor in the support matrix. They either manage windows or don't, but your app doesn't care, it just paints its window. How the user places it on the screen is his problem.