In Calc when you hit the Backspace key, the Delete Contents dialog comes up, which allows fine-tuning what kind of content is deleted, while Delete performs the default deletion (deletes everything except formatting).

Mobile virtual keyboards often only have a Backspace key, therefore on mobile it'd make sense to perform the default deletion on Backspace. The dialog could be invoked from the menu.

This is only relevant when in cell selection (so, not cell edit) mode.

This creates a small inconsistency between the behavior when working from a desktop computer or from a mobile device, but I don't think that's an issue, as it makes working on mobile more convenient.

Somewhat of an open question: what should happen if the mobile keyboard has both backspace and delete keys? I'd opt for delete and backspace working the same way on mobile regardless of the keyboard.