If you're having trouble with Launcher you can install MXL Sigma without its use.
However, you will be missing out on some Launcher configuration options and this is an unofficial method of patching D2.
Download and install Diablo II
Use "Start with a fresh install" step of the guide for reference. viewtopic.php?t=4561
Download MXL Sigma files
Launcher downloads several archives from Median XL servers
download 1.x.x.dll.update file
rename 1.x.x.dll.update to 1.x.x.dll.7z file
extract 1.x.x.dll.7z file
download 1.x.x.7z file
extract 1.x.x.7z file
Copy files into Diablo 2 installation folder
copy Fog.dll, D2Sigma.dll, MXL.mpq files
paste and overwrite Fog.dll, D2Sigma.dll, MXL.mpq files into your Diablo 2 folder
If you use Windows you should be able to run Diablo 2 normally.
Running on Mac (before 10.15 Catalina)
Install brew.sh and wine
You need to install brew and wine to run Diablo 2.
See respective guides brew.sh and Installing Wine on Mac
This guide assumes you have Diablo extracted into your home folder.
In this example it's ~/D2
For windowed mode
wine Diablo\ 2.exe -w
wine Diablo\ 2.exe -3dfx
It just works!
Common problems and solutions
I want to play fullscreen
MXL Sigma doesn't play nicely with fullscreen and DirecDraw or Direct3D. To play fullscreen you have to use 3dfx video driver.
wine Diablo\ 2.exe -3dfx
Diablo crashes with ACCESS VIOLATION (c0000005)
Make sure you're running in windowed mode (-w flag) or playing fullscreen (-3dfx flag)
Generic bad character file when creating singleplayer character
Easy way is to login to The Sin War once, create a character and log in once. After that you can create characters offline.
If that doesn't work you can create missing folder structure. $WINEPREFIX is ~/.wine by default:
mkdir -p "Application Data/MedianXL/save"
Diablo crashed and I can't close it
Use Activity Monitor.app, find and kill all wine and wineserver processes
Another option is to use CMD+OPTION+ESC combination for a force quit shortcut.
I have MacOS Catalina and nothing works
Thanks to Apple ruining 32-bit application support on MacOS Catalina it is no longer possible to run wine. There is a solution by another application named CrossOver, which is similar to wine and wineskin. You will require CrossOver version 20+ to make this work, the process is similar:
1. Create a "bottle" - a virtual instance of a Windows machine wrapper.
2. Follow instructions above to install D2 LoD + MedianXL
3. Add a shortcut to Diablo II.exe file
4. Run it with either window mode (-w) or (-3dfx)