I thought that I would create a new thread after posting this on an older thread - 'Grouping Sonos Speakers', as I have a request for some help at the end of this post.
Although there are some issues that I'm still working through, I have found a way to group Sonos Speakers from within RM.
I've achieved this by using my Harmony Hub (HH) and defining activities that select a subset of Sonos speakers. Running one of these activities removes the selected speakers from any other group they may have been included within and creates a new group. I then use the HH drivers: [Release] Logitech Harmony Hub Driver v0.1.20210725. It is then possible to switch these activities on within RM and the grouping is created.
The Use Case I was trying to achieve was to extend my TV from my Lounge to the Kitchen if the kitchen motion sensor is activated during the evening. To do this I have a rule that creates a Sonos group containing my Arc in the lounge and my Beam in the kitchen. The only issue I've not fixed is that the newly created Sonos group loses the TV input and, although the two speakers are grouped, no audio is heard anywhere! 
Does anyone have any thoughts how I can fix this little issue?
