I agree with the answer here. You can run 12 synchronously with two Corsair hubs. But I only use 6 myself. But meanwhile 4 of them already have LED errors. LED errors that always show a different colour. Digitec takes them back, but the removal is tedious and I don't want to do it. In addition, you can read on the internet that the error could come back.

The enclosed controller supports up to 6x QL fans that can play something synchronously, as I am using it.
If I understand the instructions correctly, a second controller can be added with a further 6 fans. These can all be synchronised or illuminated differently. However, I have not tested this myself.