When docs say it's still in preview and "The copilot for app users in model-driven apps feature isn't enabled by default. Administrators must manually enable this feature for their environments" ...
Found it automatically switched on across 3 environments (sandbox and prod) today.

Interestingly, the last option is set to Default which should mean only Copilot in Dynamics 365 Sales apps is enabled - however it's enabled on all model-driven apps in the environment. The default value for the second option should actually be 'Off' instead of 'Default'.

Plus, Copilot couldn't answer a single question, just keeps responding with "Sorry, I don't know that one yet, but I'm always learning."
Please don't turn on half-cooked Preview features in our environments (especially production). What a mess.