Man pages matching name fltk-config in section 1:

fltk-config.1.en	debian 10 / libfltk1.1-dev
fltk-config.1.en	debian 10 / libfltk1.3-dev
fltk-config.1.en	debian 11 / libfltk1.1-dev
fltk-config.1.en	debian 11 / libfltk1.3-dev
fltk-config.1.en	debian 12 / libfltk1.1-dev
fltk-config.1.en	debian 12 / libfltk1.3-dev