Changing (lowering) minSDK (API level) for Android Studio (2020+)

Question

How can I change the minimum SDK in an Android (Studio) project with recent (2020+) versions of Android Studio and Gradle?

During the creation of a new Android Studio project the wizard ask for the minimum SDK required.

Since the wizard generates a lot of boilerplate files and code, I assume that the boilerplate code is tailored to the minimum SDK chosen. My first objective is to generate a modern, lean, forward-compatible (Kotlin) app, so I chose API 31 (most recent non-beta on 29 Dec 2021). However, once the app (which is simple) is working, I would like to lower the minimum SDK to include as many devices as possible (without adding legacy dependencies, code, etc.). Is this a correct way to think about the relation between the choice of minimum SDK and the boilerplate code?

There are existing questions on older (2013) versions of Android Studio (and Gradle), e.g. here, but these do not work in modern versions of Android Studio and Gradle (I have only one build.gradle file and it does not mention any SDK, adding this gives errors).

EDIT: see below an image of the folder tree, as suggested.

Answer 1

Based on the comments by Ricky Mo.

The problem is that the default is the "Project View", which contains a build.gradle file that that defines the Kotlin version and the Android Studio Gradle plugin version.

The build.gradle file that defines the minSDK is found in the app folder (screenshot).

Alternatively you can switch from the "Project View" to Android. From the dropdown menu that open when you click "Project" (screenshot, highlighted).