I recently contacted the LinkedIn Sales Navigator support as in our/my LinkedIn Sales Navigator, the CRM badge opens the related CRM Contact (and Account) in the legacy interface, and there is no app selection possibility in the Sales Navigator side CRM sync admin settings. The LinkedIn support didn't seem to know about the Dynamics Unified Interface transition, and they adviced me to contact the Dynamics 365 support for solving this. Let's try this channel first.
I can see that in the CRM badge link the URL actually defines app=d365default, but LinkedIn support said they cannot help us as the problem is not in their end.
We have undergone the final "force UCI" step in our sandbox instance, and it seems that if app is not defined at all, the default app shows an alert suggesting use of an app instead. We're scheduled to receive the update on our production instance soon, and I am worried how these CRM badges will work after that. Is there (going to be) a way to define the default app for a dynamics URL?