Thank you @ivanpribec for pointing to stdlib string_type module. Unfortunately this contribution to strings from the Fortran community seems to be often forgotten/neglected (and to be honest, I am tired to always remind it to almost the same people in the always same kind of discussions).
As mentioned by @ivanpribec (or, e.g., here), I believe that stdlib_string_type module could be used as a starting point as it proposes a string_type and most of (all?) the intrinsics are overloaded for this string_type , as well as IO operations.
@FortranFan: we got your points. While I may agree with some of them, repeating them in all the threads usually result in deviating them, which does not help the discussion on the real topic (like here: strings)