It has to be the SKR Pro 1.2 that is recommended by Ryan and sold in the shop, for the others there is no compatible firmware. There are people here that got an Octopus running, but it is not the norm, so if you are starting out you should get one that works.
Maybe you could also get a Jackpot, the new board designed by Ryan himself, still from the European group buy of jackpot boards. 