8x FX engines, 4x of them with their own dedicated send buses, the remaining 4x FX engines would need to be used as inserts or channel>returns, or you’d need to sacrifice the other stereo buses to feed them ala Qu16.
Given that there are only 12x physical buttons on the console surface that provide access to the mixes, I have a feeling it’ll be fixed as 12x stereo mixes (unless you can do it with the softkeys, but there are only 8x of those on an SQ5, so not enough to access 24x mono mixes, or if there was a “shift+mix” button to press to access the odd\even side.)
Hoping some manuals are available soon.