Here's a link with a lot more information. The big news today is that the UI component for Bigscreen has just gone live as a part of the KDE 5.26 beta, which is relatively straightforward to install on any Linux distro (or image to a USB stick): https://kde.org/announcements/plasma/5/5.25.90/

Maybe the post's main link should be changed to this one? That Bigscreen website seems to be confusing and out of date.