How to enable Huawei Health app options for iOS that exist for Android?
I can't say if I just overlooked that, or if a newer version of the health app improved things: I can now see the my indoor cycling activities, too. They show up in the overview of outdoor cycling. Unfortunately, that overview only sums up distances, so the time spent on the indoor device don't count.  But at least, they all show up.
I also noticed that the user guide for another new huawei device, the Gt2 watch, explicitly mentions that certain features (such as installing watch faces from the huawei servers) only works with the android app.
But I can confirm that it is straight forward to switch the device between different phones, as I used my old android phone to install other watch faces, before connecting it with my iPhone.
EDIT: things are further improving for iOS users. In 2021, the only thing feature that I see on Android, but not on iOS: the ability to manage tracks, and those manually.