This is a guide from Reddit to run Halo Online on Linux using Wine. Still works for me but it will seem you need wine 4.18-staging version to get the game to run smoothly.

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Halo Online finally works on Linux! No more blurry transparent textures, no more black textures. This is how you get Halo Online installed manually in Wine and how to set it up Manually in Lutris.

Install In Wine

1. Install WINE and PlayOnLinux
2. Once PlayOnLinux is installed, launch PlayOnLinux and go to Tools->Manage Wine Versions
3. In the Wine versions (x86) tab, download 4.18-staging
4. Create a new WINE prefix. This is recommended
5. Launch the terminal and enter this command env WINEPREFIX="/path/to/wine/prefix" regedit
6. In the Registry Editor, create the HKEY_CURRENT_USER\Software\Wine\Direct3D\csmt\DWORD value and set it to 0
7. In the Registry Editor, create the HKEY_CURRENT_USER\Software\Wine\Direct3D\multiply_special and set it to 1 or 2 (1 has the best performance for me)
8. Close the Registry Editor
9. Open /etc/pulse/daemon.conf and replace “; enable-shm = yes” to “enable-shm = no”
10. Save the changes made to the /etc/pulse/daemon.conf file
11. Install Halo Online in the WINE prefix.

To run the game, you will need to use this command in the terminal or use this command in a launcher.

env WINEPREFIX="/path/to/wine/prefix" "/home/USERNAME/.PlayOnLinux/wine/linux-x86/4.18-staging/bin/wine" "c:\windows\command\start.exe" /Unix "/path/to/wine/prefix/path/to/eldorado.exe"

Install in Lutris (Optional)

1. Complete the “Install In Wine” steps above
2. Install Lutris
3. Once Lutris is installed, launch Lutris and click on the “+” button and click on Add Game
4. Set the name to “Halo Online”
5. Set the Runner to “Wine”
6. Go to the Game options tab
7. Set the Executable to /path/to/wine/prefix/path/to/eldorado.exe
8. Set the Wine prefix to /path/to/wine/prefix
9. Go to the Runner options tab
10. Set the Wine version to PlayOnLinux 4.18-staging-x86
11. Click Save

If you want to use your current profile ID you must place the keys.cfg file into the …/WINEPREFIX/drive_c/users/USERNAME/Local Settings/Application Data/ElDewrito/ directory.

This game will work in other versions of WINE staging but the patches that were added to 4.18-staging maybe removed in the future. These patches that make Halo Online work may work in future versions of wine that are not staging versions but time will tell weather these staging patches are added into the main wine build.