Collabora office is what I use. I do not think it has a cloud backup though.

Alternatives to Google app X for Apple’s iOS?

Google Docs would be Pages, Google Sheets would be Numbers (and there’s Keynote for presentations). Or Microsoft’s office suite for example.

Not sure if there’s a list specifically addressing what you’re looking for, but alternativeto.net probably lists alternatives for all Google apps.

What are you looking for specifically?

For offline only you can use the collabora office app or for online I recommend cryptpad, it is in a browser with no app, but it works.