I use MemeScanner and it’s great, but unfortunately not Open Source:

https://play.google.com/store/apps/details?id=com.mamsie.memescanner

this has been a thing for a few months now

They can share the same router and therefore have the same public IP.

How exactly? When using Linux, I get similar problems to those I get in Windows but in contrast to Windows, I’m able to find a solution and solve them.

In Europe (at least in the places I visited), the ground floor is 0 and the floors below that are -1, -2, … and above are 1, 2, … which makes more sense in my opinion