What are some examples of well-executed OS agnostic app design?

I've noticed some of the design conventions for iOS apps will appear on Android: E.G., Instagram uses toolbars. This also happens on iOS: E.G., Google uses material design in their YouTube Music app.

What are some examples of an app – which is designed for both platforms – that feels agnostic to either design convention, yet seems to pull it off? Thank you!

A little more backstory if needed: I'm a longtime iOS user, and now find myself designing an app for both Android and iOS. The client is requesting a more neutral UI that doesn't adhere to either OS to cut down on design/dev time.