...apologies if this has been posted before but I, for one, missed it.

Basically, they're unhappy with Sky's interpretation of the new contract, Sky's 'red button' offering and under-valuation of the Championship product in general. PL clubs get 3million each time a game is televised whilst Championship clubs get just 75,000 (sorry, no pound button on my keyboard).

Interesting, but remains to see whether it has legs:-

https://www.bbc.com/sport/football/49771802