(Official)
The 3.0.0 update for Super Mario Maker 2 Mobile includes several new features and improvements, including: Super Mario Maker 2 Mobile 3.0.0 Download - Google
A verified mobile app that lets you build, share, and play community-made arcade games safely. (Official) The 3
(Official)
Because there is no official mobile app, the community has developed several fan-made engines that mimic the experience: Super Mario Maker 2 Mobile 3.0.0 Download - Google
Super Mario Maker™ 2 for the Nintendo Switch™ system - Official site
If you do proceed with a download from these sites, you will generally end up with one of three things: 1. Fan-Made Clones