I reported this in the standard Instinct forum. Hoping Garmin can fix this in their latest and greatest version - as not working on Solar version either.
Example:
I’m currently at 17m elevation within a hike activity
i go to Hike settings>Alerts>Add New>Elevation>
I set max elevation alert to 19m
i set max elevation alert to 10m
(I get a message saying max and min are set) also Ascent/descent alerts are both off.
I walk up some stairs and watch the elevation reading go to 23m. As per using this feature on Fenix 6 - I should get an alert but nothing happens.