Also the software restrictions on the linked Netflix page seem to be arbitrary. When I download a movie in a DRM-free .mkv file, I can play it in all my browser

Also the software restrictions on the linked Netflix page seem to be arbitrary. When I download a movie in a DRM-free .mkv file, I can play it in all my browsers, all media player apps (typically VLC and MPV), and the HDMI version doesn't matter.