We might be talking about different things: one off export is possible like you mentioned but no way to sync saved links to the reading list continuously as there’re no API’s for that from Apple
On Desktop Safari the reading list is stored in a Bookmarks plist file you can grab and filter out Reading List items from, might be worth having some little desktop util for a 1 time sync to move people onto your platform? It's not ideal, but it's better than nothing.
