If you get a "Build failure" error when you try to get an output with Unity, and the explanation underneath is as in the visual above, you can use the solution method below to get your output without any problems.

First, in your project, under Build Settings;

Select and tick "Custom Main Gradle Template" and "Custom Gradle Properties Template".

# Android Resolver Properties Start
android.useAndroidX=true
android.enableJetifier=true
# Android Resolver Properties End

After you place the codes above, your codes should look like the following.

Now you can get your output without encountering this error.

By the way, if I need to mention, the main cause of this error is third-party plugins added externally, such as Google Admob.