[saltcured]

Do you have existing e-waste collection centers in your area? The local one in our county runs its own store where you can buy electronics they have picked out of the stream. Similarly, thrift stores run by local charities who take physical donations will also be repurposing electronics they receive.

I imagine that perusal of such places could give you a sense of what surplus equipment is being dumped in the community. You might even be able to chat up the workers and get a little better sense of how much waste is cherry picked versus sent onward to its destruction.

However, I also imagine these are also your competitors if you are trying to validate an idea based on collecting useful "junk" from people.