The forthcoming MacOS Sequel will have an option to use your iPhone and its apps on a Mac.

https://www.apple.com/macos/macos-sequoia-preview/

Also: Apples Password stuff has some TOTP stuff build in.

(Personally I'm a little bit depressed about the iOS-apps-on-Mac stuff - they are never good, not as Mac Apps not in general. I'd like to live in a world with better desktop apps.)