Sounds like an HDMI-CEC problem. Check the CEC adapter settings on LE's input device settings. Maybe one of those settings was resetted during the LE update.
Perfect, it was just configured towards the TV instead of towards the amplifier. I have installed libreelec many times for many years, but this time I had to do it by hand. Either with an update from 10.0.0, you are installing Libreelec from new. Thanks for the advice.