Some good news and some bad news from our side  Good news: I got the running speed from HK on my Series 4. So there is no model restriction to this metric.  Bad news: This only works when the Deployment Target is watchOS 9.0. When we set it, watchOS 8.0 will not be supported at all. Maybe this is an Xcode bug.

@jbailey Did you manage to get this working on WatchOS9? We've just been testing and can't get any runningSpeed metrics when running on Series 4 and Series 7

I also just tested on Apple Watch Series 7 and again runningSpeed was not returning any values