Man pages matching name t.rast3d.mapcalc in section 1grass:

t.rast3d.mapcalc.1grass.en	debian 10 / grass-doc
t.rast3d.mapcalc.1grass.en	debian 11 / grass-doc
t.rast3d.mapcalc.1grass.en	debian 12 / grass-doc