Tech recommendations to build Restaurant Ordering software?

we have a customer who is a chain of fast food restaurants who want us to build a food ordering app.

Is there some kind of library, API or SaaS out there that we could leverage as a backend?

I know there's a lot of ready-made apps that do food ordering, but we need to build a new frontend. Is there anything more open that we can integrate with?

We've looked at ecommerce stuff like magento, shopify & bigcommerce but they're too generic and dont really fit our use case (food). We want something that will take care of the heavy lifting (inventory management, payments, delivery management) so we can focus on the frontend. Something like Moltin but for restaurants/food would be great.

Our team usually uses Nodejs + PHP on the backend and Typescript on the frontend.