I've tried the below (it was already checked):
Try right-clicking on the executable, clicking on "Properties", selecting "Compatibility" und activating "Disable Display Scaling On High DPI Settings".

Any other suggestions? Would like to try the original before trying 1.13.

To start Jagged Alliance 2 (original) in Windows 10 you have to copy in the Game Folder:
Smackw32.dll
comdlg32.ocx (softonic.com)
(will be needed for WAE JCME you will find this on jaggedalliance.de/)
mss32.dll.

You have to delete
intro.slf

You have to install:
microsoft.com/en-us/download/confirmation.aspx?id=6812

You have to start in Folder C:\Program Files (x86)\Microsoft DirectX SDK (June 2010)\Utilities\bin\x86:
"-dxcpl-"

In the next open Window you have to click on Direct Draw
then deactivate "Use Hardware Acceleration"

You have to click on accept and ok.

After this my JA2 started with no probs and works fine.

Many thanks to [GER] The Relique Of Rage at steam
________________________________________

Zum starten von Jagged Alliance 2 (original) in Windows 10 sollte man folgende Dateien in die Spiel Directory kopieren:
Smackw32.dll
comdlg32.ocx (softonic.com)
(wird gebraucht für WAE JCME zu finden bei jaggedalliance.de)
mss32.dll

Die Intro.slf sollte man löschen.
Die Microsofterweiterung x86\Microsoft DirectX SDK (June 2010)\Utilities\bin\x86 sollten hier:
microsoft.com/en-us/download/confirmation.aspx?id=6812
runtergeladen und anschließend installiert werden.

Danach sollte man das Programm "-dxcpl-" in der Directory C:\Program Files (x86)\Microsoft DirectX SDK (June 2010)\Utilities\bin\x86 starten.

Im Fenster das sich öffnet, den Reiter Direct Draw anwählen,
dort nehmt ihr das Häkchen hinter "Use Hardware Acceleration" weg, dann nur übernehmen und okay drücken.
Das Spiel anschließend starten und freuen, daß es flüssig läuft.

Vielen Dank an [GER] The Relique Of Rage bei steam.

Someone on Bear's Pit just said he runs the 1.13 on Win10 trough DXWnd, that should work for original also, and may be worth a shot.

Another vector to explore might be Jagged Alliance 2 Stracciatella mod.

Or, use dedicated WinXP machine to run old games... I do, but that's not a solution to everyone, sure.

I just removed the intro.slf under Data folder, right clicked on the ja.exe and set it to run in compatability mode of Win XP, pack 3, reduced color mode of 16bit and under Change High DPI settings, High DPI scaling behaviour to override with Application.

No need to fix an ini file or download any files.

Remember the time when gog made old games work on modern machines? I do...