The hardware support isn’t there. The iPhone is not an open platform, so it will take a long time before there is anything worthwhile. Apple moving to their new chips on the desktop helps, but it will be a long road, and it’s questionable how much of that development will make its way back to old iPhones.

Unless you’re interested in joining a community trying to develop Linux on the iPhone, it’s really not worth it. There are thousands of better ways to go.