I have an unlimited, but slow DSL connection which I like to use for downloading. I do my normal activity through the tethered connection to my iPhone, which is fast. How can I route some apps through the DSL (which I connect to using WiFi), and all others through my iPhone (which I connect to using USB)? I also have to ensure that the downloading apps NEVER connect to the iPhone's connection. I am using macOS, but solutions using Linux are welcome, too.