What I’m aiming at here is that when my Heos Ceol (Speaker) is using source “optical_in_1” then it should ungroup the Heos group making the Heos Ceol be the only speaker active. When using any other source it should regroup. (See this thread for more info: Heos - group and ungroup rule)
Since listening to the heos player channel didn’t work* I wanted it to ungroup whenever my TV is turned on. This is the second best solution, but I would strongly prefer the checking the input source of the Heos Ceol if possible.
As far as I remember, I have tried the options suggested, but when I get back home I’ll give it another go 
*though I now know that the rule didn’t fire at all, so it might actually work once i figure out how to get the rule to fire