I am running a niche marketplace and would like to sync my Shopify customers' inventory with my website. I contacted the Sales Channel support team. They say my marketplace would not be qualified as Sales Channel App because it is too niche. I am looking into alternatives. Private app would not work because it will require me to login into each of my customer's store. If I publish as a regular App, would it be too niche too? Or can I have the app unlisted from Shopify App store and ask my customer to install it from a permanent link?
Thank you for reaching out about that. Have you already signed up as a Shopify Partner? There aren't any offline listings for the Shopify App Store, however any partner can create an app and let merchants install it. If you wish, these apps can be public, but not published to the app store. You can find out more about this in our Partner documentation here. Let me know if you have any questions!
I'd suggest getting started with this guide. It will walk you through the process of playing around with the API, and explain the difference between public and private apps. However, keep in mind that even apps on our app store need to be hosted somewhere (external to Shopify) so essentially you would need to find a host. You can find more information about that in this community post. Hope this helps!