I got a Beam + 2 One SLs to hook up to my JVC TV.
The system sounds great but it simply would not wake up when the TV was switched on. All the HDMI CEC and TV Autoplay settings were correct etc. Only thing I could do to get it awake was reboot the TV each time (or unplug / replug the HDMI cable). Not ideal.
But I think I’ve found a fix.
Also attached to the TV (by HDMI) is a Sky Q box and an old DVD player (never used but using an HDMI port all the same) so, in the name of experimenting, I moved the Sky box from HDMI1 to HDMI3 (my eARC port is HDMI2 which obviously is where the Sonos is patched) and unplugged the DVD player completely.
And now the Sonos system springs to life when I take the TV off standby.