Some admin functions, like adding new devices, can only be done from the official app.
However, for every day operation there are several different “dashboard“ apps which are very popular. Some require a paid license, some are free. They each have somewhat different features.
Here’s a recent discussion comparing them that should serve as a good introduction. Although the OP begins by asking about wall panels, these generally run in any browser and so can also be used on a mobile phone.
FAQ: Sharptools , actiontiles or native ST app for your wall panel? (2020)
note: One of the posters in that thread was @tgauchat , a developer for one of the apps. He sadly passed away last year and is very much missed in the community. If you have any questions about any of his posts, just reply to them but tag @625alex , another developer from the same company, and he’ll get you an answer.