The term "3.0.0" typically refers to the Nintendo released for the official Switch version in April 2020. Sites offering this as a "mobile download" are usually hosting one of the following:
A popular fan project often available for PC and mobile that attempts to replicate the experience for free. Mr Maker 2 Level Editor Super Mario Maker 2 Mobile 3.0.0 Download - Google
Drag-and-drop mechanics designed specifically for mobile screens. The term "3