Click at Settings -> System -> Input -> Peripherals -> CEC Adapter to setup the AVR behavior.
You listed that already as second posting and thats where i was from the beginning, see my initial posting.
Unfortunately, it does not change the behaviour, as i dont know how i should configure all those settings.
Its german, so i try to translate those entries: report kodi as primary source: checked, hdmi port number 1 and 2 (both cec adapters are configured in the same way, atm 2), wake up device when screen saver is deactivated checked, connected with hdmi-device: av-receiver, activated: checked, wake up av receiver when kodi gets activated: check, when powering off kodi report as inactive: checked, when poweroff kodi then explicit (avr + tv), on start of kodi explicit (avr+tv).
I have the feeling this is just so hardcore broken, that it does not work at all. I thought i go to the other cec adapter settings for configuration to check if they are maybe swapped (e.g. the first cec adapter is for the second port) and noticed, they are equal in also using the hdmi port which makes the possibility to configure both useless, as its only possible to configure one hdmi port, because the other entry will have the exact same configuration (including the same hdmi port). I guess thats what HarryH meant.
Is the first hdmi port close to the power supply HDMI port 1 or port 2?