Not that easily, no. With ActivityPub your user ID is tied to the instance URL. If you subscribe to a community for example, when that community tries to "honor" your subscription by sending you updates of what is happening, it'll go to that .ml domain and be lost.

There's no official supported way to change your instance domain other than to start fresh. They might be able to do something hacky such as change all of the domains in the database and while locally that might appear to work, I don't know if it would work across the federation.

I do know on the instance I run, I accidentally broke the webserver config for one of the ActivityPub endpoints and the result was that when I sent out comments, it never actually got federated / published yet I can still see them from my instance. New subscriptions also didn't work. It was as if I effectively shadow-banned the instance by accident.