CEC should work. HDMI always has the same wiring, just the cable shielding is better in higher versions.
CEC should work from HDMI 1.0 cables.
To fulfill the official HDMI-CEC specification you need cables which follows HDMI 1.2a (and upwards). Maybe your cables does already, because CEC was available for some device since 1.1, but not official. If you already tried, it could be that you have a cable, where the CEC pin is not connected and therefore doesn't work.
When LE is running, witch to TV mode, and then back to AV input.
When LE is running, witch to TV mode, and then back to AV input.
I did that, but nothing changed.
To fulfill the official HDMI-CEC specification you need cables which follows HDMI 1.2a (and upwards). Maybe your cables does already, because CEC was available for some device since 1.1, but not official. If you already tried, it could be that you have a cable, where the CEC pin is not connected and therefore doesn't work.
Possible. So you say the only way to try is by buying a newer cable? Then I hope the 12€ are not for nothing 
We still don't know your LE hardware. To my knowledge, most desktop PCs don't support CEC.
Please check CEC connectivity from SSH:
I have it's big brother (LE46C65X). It works with Anynet+ using the TV remote to control Kodi
Tested with:
ATV 4K (Jailbroken and Kodi 17.x?)
RPI4B 4GB with LibreELEC
Generic X86-64 Windows, Kodi and a Pulseeight adapter
I did that, but nothing changed.
Possible. So you say the only way to try is by buying a newer cable? Then I hope the 12€ are not for nothing
I can't make the decision in behalf of you or give a guarantee. For example I know that also cheap HDMI 1.4 cables was in the wild, which doesn't have the CEC pin connected.
Like Da Flex already mentioned right. You doesn't informed us which device you are using for LE. Because you should ensure that your LE12 device has a working CEC adapter implemented. If all things are ready, its also possible that you just chose a wrong HDMI input at your TV. Some old TVs supports CEC only at one of them.
I can't make the decision in behalf of you or give a guarantee. For example I know that also cheap HDMI 1.4 cables was in the wild, which doesn't have the CEC pin connected.
Like Da Flex already mentioned right. You doesn't informed us which device you are using for LE. Because you should ensure that your LE12 device has a working CEC adapter implemented. If all things are ready, its also possible that you just chose a wrong HDMI input at your TV. Some old TVs supports CEC only at one of them.
I also think no HDMI-cec on the device or cable. I can't be 100% sure due to a different model in the same series/generation but my TV do support sec on multiple ports (I had 2 or 3 Kodi entries in the sources menu on the TV before i figured out how to rename them in Kodi)
A very few PC's support CEC, just a couple of NUC's do that to my knowledge, so most likely your device dont.
A very few PC's support CEC, just a couple of NUC's do that to my knowledge, so most likely your device dont.
True.
None of my PC:s or graphics cards did (what's why I got the adapter - they are pricy but nice)
