I'm on Windows 10 and my other PC is a Mac. I was wondering if, on my Windows 10 machine, I can select an option to make it install the Mac version of Terraria/Garry's Mod while I'm still on Windows 10. I know that I cannot run it on Windows 10.
Yes, you can.You'll need:
Target platform (Windows, Mac, Linux).
Target architecture (32 or 64-bit).
With Steam fully closed, run it with the
-consolestartup option, or click steam://open/console (Steam Browser Protocol shortcut).
Go to the Console tab and type the following commands (and press Enter at the end of each):
@sSteamCmdForcePlatformTypetype (where type is windows, macos, or linux)
@sSteamCmdForcePlatformBitnessbitness (where bitness is 32 or 64)
Download the app or game normally.
3a. If you need to close the Steam client for any reason, try pausing the download and removing it from the download queue to attempt to prevent the issue in 3b.
3b. If the download is active while the Steam client is restarted it will switch to downloading for the default system, likely destroying some downloaded data. In my test years ago this caused Payday 2 for Windows to become the PD2 Soundtrack for Mac. Running the commands in step 2 again and pausing and continuing the download fixed it.
After step 2 you're running the target machine as far as the local Steam client is concerned. Any games you have installed for your default system may not start (missing executable error) or may not run well or even break something if you try to run them.
When you move the install data also move the appmanifest_#.acf (where # is the Steam appid), unless the machine you're moving it to has internet and can handle having to verify the installed app (by starting the install and letting Steam find and verify the existing data).
The Steam client console essentially uses SteamCMD internally, which is a bare-bones Steam client for the terminal that could also be used for this purpose.