This specific distribution is known for being very weird in general. As such, some of the later passages may be a little off compared to your OS, but that's okay! You should be able to find out any issues from the Internet, as most of the problems will be related to installing Protontricks.

Also, this guide is not a complete index of everything wrong with Linux C&C and how to fix the problems. As they crop up, I will attempt to cut down these problems and break them down as best I can.

I am welcome to any and all feedback on the guide, as well as constructive criticism.

Thanks,
Wren

Steam on Linux runs quite differently to Windows, as it uses a fork of the Windows program compatibility layer called Wine (which stands for Wine Is Not an Emulator). This fork is called Proton, and will be referred to as such throughout the entire guide.

Click Steam in the top-left, then click Settings, as depicted.













After that's done, go to Steam Play, and enable the Proton compatibility layer if it isn't already, after which, enable it for all games. Choose Proton Experimental as the default version. Hit ok and exit.

This is because C&C3 launches with a specific set of options by default that isn't exactly agreeable to Proton, and so, when attempting to unfocus the window, the game will immediately crash. This can be solved fairly easily; first, navigate to C&C3 -> Properties.

After you have done this, change the launch options to include the following flags:




Doing this will practically get C&C3 to stop complaining, and it should not crash from there on out. You may have other issues, however.

This is because you don't have DirectX 9 installed for Proton. Here, I would suggest forcing an older version on C&C3, this time using compatibility options. Here, I will use 5.13-6.


After this is done, and if it didn't solve the problem, well, we're going to have to get a little... tricky.


Quick reminder: I'm using Gentoo Linux. The steps to install Protontricks will differ per OS, but Gentoo has it in Portage's default package repo.
With that disclaimer out of the way...
First, boot up your terminal emulator. Check to see if protontricks is already installed. For fellow Gentoo users, use the following command:





as depicted to the right. If it's installed, skip the next step. If not, run the following command:




Unmask any packages, if necessary, then type yes. It'll most likely fetch a bunch of other packages, such as Winetricks, as it is simply a Winetricks wrapper.

Once Protontricks has finished installing with whatever package manager you use, merely run the following terminal code:








Once that's done, your unit problems should normally be solved. Try to boot the game again!