Ok, I've gotten rid of dub and dub packages code. Just LoadLibraryA. All eight dlls work except for FreeImage.dll. I've compiled with dmd and -m64 option and freshly download a x64 FreeImage. Any Window users out there that use LoadLibraryA or FreeImage.dll?

import std.stdio: writeln;
import std.string: toStringz;
import core.sys.windows.windows: LoadLibraryA;

void main()
{
    string[] DLLs = [ "assimp.dll", "fmod.dll", "freetype.dll", "glfw3.dll",
                      "OpenAL32.dll", "SDL2.dll", "SDL2_mixer.dll", "FreeImage.dll" ];
	
    foreach(dll; DLLs)
    {
        void *ptr = LoadLibraryA(toStringz(dll));
        if (ptr)
            writeln("calling LoadLibraryA with ", dll, " ptr is set");
        else
            writeln("calling LoadLibraryA with ", dll, " ptr is NULL");		
    }
}

C:\Users\Admin\Documents\GitHub\Delivery\apps\00_03_freeimage_debug>app.exe
calling LoadLibraryA with assimp.dll ptr is set
calling LoadLibraryA with fmod.dll ptr is set
calling LoadLibraryA with freetype.dll ptr is set
calling LoadLibraryA with glfw3.dll ptr is set
calling LoadLibraryA with OpenAL32.dll ptr is set
calling LoadLibraryA with SDL2.dll ptr is set
calling LoadLibraryA with SDL2_mixer.dll ptr is set
calling LoadLibraryA with FreeImage.dll ptr is NULL

C:\Users\Admin\Documents\GitHub\Delivery\apps\00_03_freeimage_debug>dir

03/22/2023 01:45 PM 3,116 app.d
03/22/2023 01:46 PM 681,984 app.exe

03/06/2023 04:25 PM 3,805,184 assimp.dll
03/06/2023 04:25 PM 1,721,344 fmod.dll
03/06/2023 04:25 PM 6,942,208 FreeImage.dll
03/06/2023 04:25 PM 832,512 freetype.dll
03/06/2023 04:25 PM 216,576 glfw3.dll
03/06/2023 04:25 PM 122,904 OpenAL32.dll
03/06/2023 04:25 PM 1,220,096 SDL2.dll
03/06/2023 04:25 PM 143,872 SDL2_mixer.dll

On Wednesday, 22 March 2023 at 19:33:45 UTC, WhatMeWorry wrote:

import std.stdio: writeln;
import std.string: toStringz;
import core.sys.windows.windows: LoadLibraryA;

void main()
{
    string[] DLLs = [ "assimp.dll", "fmod.dll", "freetype.dll", "glfw3.dll",
                      "OpenAL32.dll", "SDL2.dll", "SDL2_mixer.dll", "FreeImage.dll" ];
	
    foreach(dll; DLLs)
    {
        void *ptr = LoadLibraryA(toStringz(dll));
        if (ptr)
            writeln("calling LoadLibraryA with ", dll, " ptr is set");
        else
            writeln("calling LoadLibraryA with ", dll, " ptr is NULL");		
    }
}

Most likely a dependency that is missing?

Can you zip your folder and upload it somewhere so i could try help you debug this issue?