Was HDMI-CEC not an option here? Particularly considering a Raspberry Pi is involved.
My personal experience with cec-utils is that device support is hit or miss.
I tried controlling a TV a while back, and I think I could get it to turn on, but not standby or off.
Worth a shot though.
(I do think his project is pretty cool, and it shows people that they can regain control of their dysfunctional iot devices)
What a polite way to say it.
CEC and DDC-CI, are these two things that should be absolutely nailed given in terms of low level commands how simple they really are and how long they've been around, yet are thoroughly broken through and through in so many subtle ways, from broken payloads to timing issues.
And even when the low level protocol is correctly implemented you can be sure that the high level behaviour of the devices is not doing what you'd want it to, with no workaround possible.
e.g one device turns -all- devices on/off no questions asked, another would not allow separate configuration of being controlled vs controlling, and/or power on vs power off, a third one would disable CEC the moment you select headset audio output because it goes in the way of their MegaMagicSync+ feature (which is just CEC with a bunch of useless proprietary stuff to talk to other devices of the same brand, coz gotta "add value" and "differentiate")...
It's probably too late for HDMI-CEC, there are too many crappy pieces of hardware out there. I'm just wondering what stops this from happening next time. It's a great system when it works and so much better than trying to reverse engineer other protocols. Just a shame that it's so bad it doesn't even get a mention in a post like this where it should have been the perfect solution.
Relatedly, does a £300 soundbar in 2020 still only come with one HDMI input!?