This is something I want too, but I've run into these issues:
1) The MCU solution as presented here is software based aka "As it runs, the software performs a continual series of screen captures, averaging the pixels in blocks around the perimeter of the screen and issuing the resulting color data to the LEDs." a program runs on your supported OS PC and consumes CPU etc. to capture frames, average and control the LEDs. = lost performance, may as well be running OBS capture in background all the time.
2) pass through solutions exist but are often limited to 1080p60 HDMI only and no 4k120+ DP that one likely wants for PC use.
3) that janky camera solution to avoid doing on PC capture or HDMI/DP pass through and processing. I can't imagine this one being any good, fast, accurate.
The LEDs can be bought as strips almost anywhere, it's the same LEDs or 2 type, WS2812, 01 or such, search and it's easy to find, programmable LED strip, or digitally controlled LED strip. I wouldn't bother with some individual LEDs that one has to connect, just buy a strip and to cool it attach it to a piece of aluminium profile. Get any controller the open source software you can get supports, or get some proprietary one, and that's it. No need to buy expensive pre-selected parts packs, single LEDs, etc. There are a lot of sellers, sites to get these things in last 2 years as the programmable LEDs got very easy to buy.
I'm using a static high CRI LED until a proper pass through DP/HDMI solution is available and affordable.
The capture ones are "cool and easy" but I don't want the performance penalty of screen capture 24/7
If it can even capture everything and all the time as that also takes some doing on the software side and even dealing with anti cheat for games so the program is white listed.