The general feeling has been that hardware questions are okay provided they are unique to Android or a specific Android device in some way. The one that you've linked to seems okay in my opinion since the OP specifically notes:
The cable in the above link successfully transmits audio from one
iPhone to another.
But for some reason it fails on my Android device.
Therefore, the question is - to me - specific to Android. Since the cable works for two iPhones it's reasonable to infer that the Android device behaves differently and must be treated differently.
Also, questions of that sort are probably not appropriate for the Electrical Engineering site since it's essentially dealing with how to use the cable (the question the OP linked back to discussed how to build it). I find the domain to be a little bit misleading since there was a different electronics site that originally dealt with consumer-type questions (Gadgets). However, that site was closed, and we actually subsumed many of their questions. Electrical Engineering is for more high-level stuff, and notes in its FAQ (emphasis mine):
We feel the best Electronics Design questions have a schematic, links
to pertinent datasheets or some C code in them, but if your question
generally covers …
- a specific electronics design problem
- the theory and simulation of electromagnetic forces
- a communication scheme
- the writing of firmware for bare-metal or RTOS applications
and it is not about …
- a shopping or buying recommendation
- consumer electronics such as media players, cell phones or smart phones, except when designing these products or modifying their electronics for other uses
- Programming software for a PC