"Sharing internal / cache images (with text) to other Android apps" (tutorial at https://blog.jakelee.co.uk/sharing-internal-cache-images-with-text-to-other-android-apps)

AndroidManifest.xml

<provider
        android:name="androidx.core.content.FileProvider"
        android:authorities="${applicationId}.fileprovider"
        android:grantUriPermissions="true"
        android:exported="false">
    <meta-data
            android:name="android.support.FILE_PROVIDER_PATHS"
            android:resource="@xml/filepaths" />
</provider>

filepaths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths>
    <cache-path name="shared_images" path="/images/"/>
</paths>

MyFragment.kt

fun shareImage(file: File) {
    val authority = "${BuildConfig.APPLICATION_ID}.fileprovider"
    FileProvider.getUriForFile(context, authority, file)?.let {
        val shareIntent = Intent()
            .setAction(Intent.ACTION_SEND)
            .addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
            .setDataAndType(it, context.contentResolver.getType(it))
            .putExtra(Intent.EXTRA_STREAM, it)
            .putExtra(Intent.EXTRA_TEXT, "I'm sharing this image!")
        context.startActivity(Intent.createChooser(shareIntent, "Share image to:"))
    }
}

val imageCache = File(context.cacheDir, "images")
shareImage(File(imageCache, "myimage.png"))