: There are technical guides on how to make the FieldTest application icon permanently visible on jailbroken devices. 2. Starfinder & Pathfinder RPG (Paizo)
If you are trying to find the hidden menu on your iPhone to check signal strength or LTE bands: Fieldtest
: Users on Reddit r/cellmapper often post updates about changes to this interface in the latest iOS betas. : There are technical guides on how to