From some research it seems that hercules was actually supported:
https://www.dosbox-staging.org/getting-started/enhancing-pri...
and from
https://dosdays.co.uk/topics/Games/game_prince.php
> Intel 8088/8086 CPU, 512 KB of RAM (640 KB for MCGA/VGA version) Graphics support for Hercules, CGA, Tandy/PCjr, EGA and MCGA/VGA (320 x 200 max. resolution in 256 colours)
Notice that PoP was one of the few games I was able to play with that hercules monitor :|