It works natively in Xbox 360 mode on the PC in SF5 as it’s fully X360 xinput compatible. Make sure you install the xbox 360 Microsoft drivers. The Q4raf then functions identically to the real Xbox 360 controller (even the “RS” axis (X and Y rotation) appears, although you can’t use it).
On a PS4, It can work as a “legacy” controller when set to PS3, I believe, but that depends on what it’s seen as. If it’s seen as a dual shock 3, then it might not work. You’ll have to read the threads about PS3 fightsticks on PS4 in legacy mode for more information on that.
It works perfectly with a PS3 to PS4 Brook white converter (if you wind up with any extra input lag, ask the Brook engineer for the beta firmware; this fixed the 0.4ms lag another user was having completely).
It also works perfectly with the Brook UFB, but that’s a rather expensive PCB mod. You can wire the “PS3/PC” toggle switch switch on the Qanba to the “LS” pin on the UFB to regain DP/LS functionality (only really needed in much older games).