Ok I'm TOTALLY baffled.
So on ttnctl subscribe and on mosquitto_sub I am getting just one message for 02011E07 and nothing for any of the other devices. To get another message for 02011E07 I need to re-register it.
However, I am looking at the good old v0 api web pages and seeing the messages regularly appearing for all 3 connected devices. ...and yet the good old v0 mqtt thing is showing nothing at all.