Do you need HDMI to HDMI (video) + {optical or RCA}?
If you are looking for something else (e.g. eARC), then you should be looking for a different device.
Note that not all HDMI Audio Extractors support 4K HDR, HDMI 2.0, HDCP 2.2 (or better). Look for that in the description. Devices build on the HDMI 1.4 standard are not suitable for commercial 4K content. You’ll probably want HDMI 2.0 or HDMI 2.1 based devices.
Note that most modern TVs can do audio passthrough quite well. Then you wouldn’t need an Audio Extractor at all.
I don’t use an HDMI Audio Extractor myself, so I can’t recommend one. I hope one of the other readers can?
I already tried one, but it did not work.
Can you elaborate? What didn’t work? What happened instead?