Add some comment

vector/src/main/java/im/vector/riotx/core/utils/ExternalApplicationsUtil.kt

@@ -70,6 +70,8 @@ fun openUrlInExternalBrowser(context: Context, uri: Uri?) {
 
 /**
  * Open url in custom tab or, if not available, in the default browser
+ * If several compatible browsers are installed, the user will be proposed to choose one.
+ * Ref: https://developer.chrome.com/multidevice/android/customtabs
  */
 fun openUrlInChromeCustomTab(context: Context, session: CustomTabsSession?, url: String) {
     try {

vector/src/main/java/im/vector/riotx/features/login/LoginSignUpSignInSsoFragment.kt

@@ -43,6 +43,7 @@ open class LoginSignUpSignInSsoFragment @Inject constructor() : LoginSignUpSignI
 
         val packageName = CustomTabsClient.getPackageName(requireContext(), null)
 
+        // packageName can be null if there are 0 or several CustomTabs compatible browsers installed on the device
         if (packageName != null) {
             customTabsServiceConnection = object : CustomTabsServiceConnection() {
                 override fun onCustomTabsServiceConnected(name: ComponentName, client: CustomTabsClient) {