Configuring a pop-up with a custom attribute display to launch Survey123 for ArcGIS app or Collector for ArcGIS app from Explorer for ArcGIS (Android) failed.
This issue is non-reproducible in 18.1.0 version of Explorer. There are other issues when using field substitution to pass in values to a URL which can be worked around. There are also issues where plain URLs cannot be tapped on Android OS