pfr, I get so tempted to do your "Oi!" trick to fellow pedestrians. My "Oi!" might not be manly enough to do the trick, though. LOL

I had a similar experience to your example 2b. I was walking up a sloping path leaving a city park, and heading for the street footpath. Every person I saw either coming down the path, or walking along the street footpath had their head down looking at their phone. Mostly young people. Possibly uni students because the city campus is nearby.

But even older people do it. I very nearly did the "oi" trick to a middle aged woman this week. She was walking straight towards me. I was tempted to just stand still and wait for her to run into me.

But maybe the phone phenomenon is bleeding into everyday life. Twice this week when I was driving, and within a few minutes of each other, two people just started walking across the road right in front of me without checking for traffic.