The game actually has a menu for changing the controls, but it doesn't seem to work.

You're supposed to be able to Press M to modify or E to End and while E does work, M doesn't.

Any ideas? The default controls are terrible.

For the German Keyboard "ö" worked as a replacement for M
The keys for formation seems to be STRG but I haven't been able to jump...

Regular keyboard it's the ";" key.

For Hungarian users: on Hungarian keyboard, the "M(odify)" key is "É".

Up, Down, Left, Right, Fire, Retreat
There are controls for player 1 and 2, you can also use a joystick, in the North and South directory, there are manual and reference card pdf files.
Notes from a U.S. player:
how to switch which active army type you have selected: You can only control either Artillery, cavalry, or infantry at once. You can tell which type you have selected by the top left icon. (Cannon balls, Horse, and rifle) For the LEFT player it is the LEFT SHIFT key, and for the RIGHT PLAYER, it is the RIGHT SHIFT KEY.

There is also an arcade mode.

Edit: Got controls switched, but mouse directional controls work.
My controls were in german so after setting up , I did: ; to start modifying controls f to quit and o to confirm

Found how to set languages: I think the 3 flags at the beginning, before the main menu are for languages, the one in the middle may be the Britain flag, for British, other languages may be Hungarian and German

The manual seems to list more keyboard commands... Page 6 shows how to pick number of players: 0-2.
I was able to turn sound off with F9

I can select items with mouse.
escape works.

Updates:
Found out you click a blinking area to move there after you click on a guy when starting.
Changed keyboard layout from auto to a specific country in dosbox_ns.conf
'keyboardlayout='
examples:
fr gr hu us be uk

reference: https://www.dosbox.com/wiki/KEYB