Thank you for reaching out to the Community! I'm happy to provide some assistance with integrating apps into the shop, to ensure this gets resolved. To confirm I'm fully understanding, are you looking to add an app from the Shopify App Store?
After taking a closer look, it seems the app Flutter is not currently available within the Shopify App Store. Due to this, you will want to connect with the third-party app directly for clarification on its ability to be integrated into Shopify.
Their support team will be able to provide additional details on this, as well as assistance with the integration process. For ease, I've gone ahead and included theirSupport Pagefor you to connect with!
Please let me know if you have any other concerns.
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