If you need to disable automatic fulfillment, we have a handy checkbox for this! However, you may want to read this first. In general, even MFN sellers usually should not disable automatic fulfillment, as then we won't notify you of sales.
This option can be found in your Advanced Settings.
You can disable automatic fulfillment for both eBay and Shopify as needed.
See below screenshots for reference to disable for eBay and Shopify