I got it working by:
Going to Settings on my M2 Mac mini
Scrolling down to and selecting ‘Privacy & Security’
Selecting ‘Local Network’
Strangely enough, ‘Zwift’ was included in the list already, and the toggle was activated. But after I switched off the toggle, waited for a few seconds, and switched it back on again, the companion app switched to ‘map mode’.
Hardware:
M2 Mac mini, macOS 15
iPhone 13 mini, iOS 18