You always own your intellectual property, mailing list, and subscriber payments. With full editorial control and no gatekeepers, you can do the work you most believe in.
Oh my mistake—I wrongly assumed you had started on Substack. (Many people do, since it’s free to start here.)
You can certainly take all 11 of those subscribers with you. If some have email disabled, it’s likely because they prefer to read posts in the app, since for many that’s a better reading experience than email (some people prefer not to have posts mixed in with emails from grandma or the bank). But you still retain their email addresses. That audience is yours—you can export it. And since you aren’t actively publishing posts here (and I assume no one is recommending your test publication), they must have become your subscribers through the Substack network. So, you got those subscribers thanks to Substack. I hope you will treat them nicely.