For OsmAnd offline map specifically, you can go into hamburger menu, select Configure map, click on ... on POI overlay... entry, click Search, type in communication tower and select SHOW ON MAP below it. That will show all mapped communication towers on OsmAnd map as orange circles (with tower picture inside them).
(or you can of course select nearest tower instead and click Navigation button to navigate you directly there)
As how well are man_made=communications_tower, tower:type=communication and their ilk mapped on OSM, depends on the region (only some 16% or so have operator mapped, though).
You can always map additional ones (even using OsmAnd’s OpenStreetMap editing plugin; although apps like Every Door or SCEE might be more ergonomic, or Vespucci might give you more power instead if you prefer that)
