Thanks to Peter Gorvett for this –
If you enjoy seeing other runners’ routes after a race or club run, Strava Flybys are great. But after a social media storm, Strava changed the default setting so they are disabled for all users. To see them or for others to see you, you need to change the default back.
More details at https://www.dcrainmaker.com/2020/10/strava-flyby-turns-feature.html