According to the current consensus on Meta, questions about printers are on topic, even questions concerning the hardware. Also, according to the help, it is OK to ask question concerning smartphones "insofar as they interface with your computer". The same has been said on Meta as well.

However, I've just asked (and answered) a question regarding setting up a printer so that it is correctly found on the network by smartphones, and I get instantly voted down. Firstly, if it is off topic, shouldn't it be suggested to be closed instead of being downvoted? Secondly, if it's off topic there, then where is it on topic? The problem is with the printer, not with the Android device, and if I ask the same question on Android Enthusiasts, it will be closed for sure. It doubt it will connect with an iOS device either, for that matter. So are questions which ask about setting up connection of your peripheral equipment with other devices on topic?

Honestly it's very discouraging when you take time to write down an answer to the problem that has been pestering you for weeks and immediately receive a negative reaction just because your problem with a printer happens to also involve an Android device.