It’s kind of a bad tutorial if you ask me, working completely backwards like that - best thing about it was probably the little snipped of Roundabout :D. Starting with a group? Never seen that before, you group things when everything is done. Not doing previews of the signal (hard to do when inside a group). Not showing the UV. Incoherent scales - even the example shows this.
I was able to make it “work” by tweaking the color ramps (which could have been math nodes in this case) and adjusting the last brick settings. And of course the groups strength setting should not be zero.
Although it is great for practice, unless you want an extreme close up of a display, you would ignore all that stuff and go simple. Let me know if you want to see a completely different approach to this, although a lot more complex. Presenting displays (in use) is what I do (or, in these times, did) prefessionally, so I set it up as best as I could. Of course, I would always turn it off and bypass the whole system because it’s never actually needed. But I had to set it up, lol.