I have now looked at the topic Ambilight again and would like to start a new project. So far so good. I still have an old LED Ambilight kit from AliExpress with an Arduino Uno Box. The LED strips are connected by cable without soldering. Just have a look here: https://de.aliexpress.com/item/32900964704.html
Isn't it possible to use Hyperion via the Raspberry (with HDMI Grabber and the whole other stuff) and connect it to the Arduino box? Then you could save soldering the LEDS to the Raspberry.
HDMI --> splitter etc. --> Raspberry with Hyperion --> Arduino Box (from the kit) --> LED (from the kit) WITHOUT soldering
I hope you understand what I mean. I'm happy about every suggestion for a solution.