I tried using four different HDMI grabbers.
All of them were purchased from AliExpress.
1.video capture with loof - hdmi-cec (x) rainbow signal (o)
2.video capture 3.0 - hdmi-cec (o) rainbow signal (o)
3.RULLZ video capture 2.0 - hdmi-cec (o) rainbow signal (o)
4.video capture 2.0 - hdmi-cec (o) rainbow signal (x)
Grabber four turns off the TV and the led goes off at the same time.
I am currently using product number four.
It's working very well.
https://blog.naver.com/lomazzi/222328138535
Product No. 4 Link
It is a black 2.0 product