This is Lana from Shopify. That's a great question!
If you're not based in a country that is supported in Exchange Marketplace, then you will be able to sell your store by dealing with the buyer directly. In terms of finding a buyer, that would be entirely up to you since you won't be able to publish a listing on exchange, and all dealings from then onwards would be between you and the buyer.
Please do note that when selling outside of Exhchange Marketplace, we are unable to support you or intervene if there is conflict or any kind of issue there.
Also, what country are you based in? This may be of importance in terms of being able to follow all regulations related to selling your business, so I would recommend you research this locally as well before making the sale.
Once you have an agreed sale, you will want to transfer ownership to the new store owner. This needs to be done manually by you because again, we are unable to assist in this process. Transferring store ownership is done the following way:
From your Shopify admin, click Settings, and then click Users and permissions.
Click Add staff.
Enter your staff's full name as it appears on any government-issued ID, and their email address.
Click Send invite.
Go back to Users and permissions.
Click Transfer ownership (top right hand corner above where your name is).
Enter the email of the new store owner. If the new store owner isn't existing staff, then you need to enter their name, too.
Enter your password to confirm the change.
Click Transfer store ownership.
If your store has any social media accounts, you may want to hand them over to the new owner as well just so that they can continue operations of the store as normal.
Let me know if you have any other questions.