I had this issue and one of the libraries I used wasn’t setting it correctly.

Find location

First of all, we need to find the exact location and/or cause for the error,
which can be done with different approaches (see below).

Find by inspecting merged-manifest ^{(approach #1)}

You can find it by doing the steps:

• Set target SDK to 30 (to silence 31+ errors).

• Open application’s manifest (AndroidManifest.xml) and click on “Merged Manifest” tab on bottom of your edit pane:
  

  Which if you configure build.gradle like:

  allprojects {
     buildDir = "${rootProject.rootDir}/build/${project.name}"
  }
  

  Something similar should be in a sub-path like:

  build/my-app/intermediates/merged_manifest/debug/AndroidManifest.xml
  

• Go to the individual manifest file of all the libraries (You can skip this step if the merged manifest is created and you can just look into the merged manifest)

• Search if there’s any entry of type activity, service, receiver, or provider which does not have an exported attribute, and for each entry follow below “Fix found entries” section (or see once for how to set exported attribute).

• Set target SDK back to 31 (or whatever it was before changing to 30).

Find by console logs ^{(approach #2)}

• In Git-bash run something like:

  ./gradlew assembleDebug --stacktrace --info | tee my-logs.txt
  

• Open my-logs.txt file (which previous step created, in your preferred text-editor).

• Now, the exact location is hidden in the logs,
  hence search in the created my-logs.txt file,
  for these keywords:

  • activity#
  • service#
  • receiver#
  • provider#

• Which should find something like:

activity#androidx.test.core.app.InstrumentationActivityInvoker$BootstrapActivity
ADDED from [androidx.test:core:1.2.0] C:\Users\Admin\.gradle\caches\transforms-3\709730c74fe4dc9f8fd991eb4d1c2adc\transformed\jetified-core-1.2.0\AndroidManifest.xml:27:9-33:20

• Open AndroidManifest.xml file that previous steps did find, search if there’s any entry of type activity, service, receiver, or provider which does not have an exported attribute, and see below “Fix found entries” section (for how to set each entries exported attribute).

Note that (at time of writting) passing --stacktrace alone did not include location info 😉

Fix found entries

If the real (not build-generated) source of found entry is in root-project’s manifest (or somewhere you can alter),
set exported attribute to corresponding need (which is normally false) therein directly, like:

<receiver
    android:name="<name_of_the_entry>"
    android:exported="false or true"
    tools:node="merge" />

Note that both android:exported="..." and tools:node="merge" are set above.

But if found entry’s specification is written in the manifest of a third-party library (which’s real-source you can’t alter),
override the specification of said library by adding it to our root-project’s manifest, for example like:

<provider
    android:name="com.squareup.picasso.PicassoProvider"
    android:exported="false"
    tools:node="merge"
    tools:overrideLibrary="com.squareup.picasso.picasso" />

Note that this time tools:overrideLibrary="..." is set as well.

For more information see Documentation,
and/or Similar issue in a SDK.