The logic which decides if a device enumerated via the direct input system in the function EnumJoysticksCallback in SDL_dinputjoystick.c is processed is discarding valid joystick devices due to the assumption that devices of the type DI8DEVTYPE_SUPPLEMENTAL are not valid devices.

This change was added with 2.0.4 with this commit http://hg.libsdl.org/SDL/rev/d5adc0c06a03 that is linked to this bug report https://bugzilla.libsdl.org/show_bug.cgi?id=2460 which indicates that in that case devices of the type DI8DEVTYPE_SUPPLEMENTAL were not desirable as they caused a singular device to emit multiple "device added" events.

Since then there appear to have been a few fixes to handle devices that fall into various other classes in the following two commits: 
http://hg.libsdl.org/SDL/rev/b9488c689ce3 and http://hg.libsdl.org/SDL/rev/161fee58e36f

Two devices I have reports of failing to be listed when the DI8DEVTYPE_SUPPLEMENTAL type is excluded are ECS Gametric Throttle and Thrustmaster MFD Cougar.

I'm unsure what the best or most desirable solution to this is as the initial change had a particular purpose, however, it also interfers with devices being properly listed that windows itself considers joystick devices. One way probably would be having a different logic to detect when a single device emits multiple "device added" events, however, I'm not familiar enough with the internals of direct input to say if that's even possible to detect.