@sartoric I tested other iOS apps on macOS, and they work perfectly.
The Suunto app also functions across three screens, as long as you don’t log in.
However, as soon as you log in, the app successfully navigates to the activity screen and works fine—for that one session. Once you quit the app, it fails to start again (maybe because the initial setup views are skipped?).
I shared this information as part of my follow-up email in response to my support chat.