Hey, there

You can use smart segments to automatically list items in a desired channel. Items will be removed from the channels based on the store settings. For eBay, you can disable the 'Listings stay active when out of stock' feature if it's enabled for your store. So the item will be automatically ended after being sold. You can learn more about this here: https://www.ebay.com/help/selling/listings/listing-tips/bulk-listings?id=4160#outofstock