Stu: Have a look at https://play.google.com/store/apps/details?id=app.defaultappmanager.pro to see all defaults (not all defaults can be seen under the Default apps configuration in the app manager (hit the three dots in the app manager))
Set Google Contacts as your default contacts app and configure it to show just the contacts you want to see. Turn off contacts sync for all other accounts. Hide the Samsung contacts app in your launcher.
The 'share your profile' text isn't there to annoy if you hit 'contacts' within the phone app.
Ah thank you. I thought that I should be able to change defaults in the main default settings, not need another app to do it.
And yes, now I can choose a default Contacts app.
But the Contacts app in the Phone app is still the Samsung one. It's clearly hardcoded. But as you say, the annoying "Share your profile" is not present there, when opened via the Contacts in the Phone app.
Thanks for your pointers. It's all useful to getting clues about how it's all supposed to work.