hello, i have research for this problème but i can't résolve it..
i have try to édit dosboxhomm2.conf
i have test 0x0 1920x1080 1920x1440 etc..
i have test all scaler.. all output.. even fullfixed=false or true

all time this game have black border on full screen
and on windowed the window is small (the empty space is the same as the black border)
on 1920x1440 on windowed it takes up all the space of the screen, but the game is zoom
and on full screen this game return on 1920x1080 (more = crash)
if someone would have a solution
thanks in advance and sorry for my bad english :c

You must change scalling mode in your graphics card settings.

i have try with fullscreen and validating replaces the scaling mode defined by games and programs
but not work :(

Don't you have something like "maintain aspect ratio"? Try selecting this option.

no i don't have that or I didn't find it
i have GTX1070 if it helps

You should have something similar to this image:

oh yeah, in the beginning he was like that and suddenly no work too :(
I don't understand why is don't work :'(

on first message I put capture black border that I have and the size of the window on windowed mode (who are not on the scale because of the size 500 ko limit)

You will always have black borders on left and right because the game was designed to be displaying on 4:3 monitors. That's the feature of old games. Of course, you can set "Full-screen" option in your graphics card settings and the game will scale, but this won't be orginal resolution. I think that having borders is better option, but it's your choice.

I want to scale it but it does not work :(

Stretched horizontally Heroes 2 IMO looks awful, but if you really want it, just change "Aspect ratio" option to "Fullscreen" ("Plein écran" in French). If that won't work, I can't help you.