Power Apps - [Recommended Change] StartScreen recommended instead of OnStart.
The OnStart property has been used to improve performance, and its main uses are the following two:
• Data caching settings
• Global variable settings
Because OnStart is executed before the screen loads, it can potentially cause unforeseen problems during development. As a solution, we recommend using StartScreen, as shown in the upper right image.
While some ingenuity may be required during development, please consider using StartScreen.
This video explains the procedure, including setting the property.