I recently started playing SimCity 4 again and came upon this wonderful community. Thanks everyone!
Like many others, I couldn't get any of the pre-baked Mac installers to work, but I did manage to get one of the basic installations working, by running the Windows installer in a VM and copying the files over. Here's what worked for me; hopefully it will work for you too.
My Setup
Macbook Pro (16-inch, 2019)
MacOS Catalina 10.15.3
SimCity 4 from the App Store, version 1.2.1
How to install Windows 10 in a VM
I found these two youtube videos, which described how to download a Windows 10 installer ISO and VirtualBox, and then configure them: https://www.youtube.com/watch?v=uUx8Y5Kj_hs and https://www.youtube.com/watch?v=qUfWTYkj4Q0 . The instructions are roughly:
Download a Windows 10 ISO from Microsoft: https://www.microsoft.com/en-us/software-download/windows10ISO
Download VirtualBox: https://www.virtualbox.org/ (I'm using version 6.1.6)
Create a VM in VirtualBox, and point it at the Windows 10 ISO to install. Wait a while for the installation flow.
When prompted for an activation key, click the "I don't have one" button, and proceed normally through the rest of the installation.
At this point, Windows is working, but there's no easy way to transfer files between the Windows VM and the host Mac. You need to install some Windows drivers:
With your Windows installation running, choose Devices > Insert Guest Additions CD Image ... from VirtualBox's menus.
Inside Windows, navigate to the CD Drive ("This Computer" > "CD Drive (D:) VirtualBox Guest Additions") and launch "VBoxWindowsAdditions". Install everything.
Reboot the Windows VM.
Creating a shared folder between Mac and Windows
Somewhere on your Mac, create a folder to be used for copying files back and forth. It doesn't matter where. I put something in my "Downloads" folder.
In VirtualBox, choose Devices > Shared Folders > Shared Folders Settings ...
Add a new folder. Choose your shared folder as the "Folder Path", give it a name for Windows (I used "W10_Shared_Folder"). Read-only OFF; Auto-mount ON; Make permanent ON; and leave mount point blank.
You should now see "W10_Shared_Folder (\\VBoxSvr) (Z:)" under "My Computer"
Installing NAM and copying the installed files
I downloaded NAM36 for Windows on my Mac, and dropped the zip file in my shared folde r.
On the Windows side, I navigated to "W10_Shared_Folder", opened NetworkAddonMod_Setup.zip, and ran the installer straight from it.
To start with, I chose the "Traffic Simulator and Maxis Fixes Only" setting. And I answered "Yes" to "Is this going to be copied to a Mac?".
Once this was done, I went to my "Documents" folder in Windows, and copied the whole "SimCity" folder to "W10_Shared_Folder".
And now I had all the goodies in the Mac side. Woot.
Installing the results into SimCity 4 on Mac
I'm using the AppStore version, so my Plugins folder is under (home)/Library/Containers/com.aspyr.simcity4.appstore/Data/Documents/SimCity 4. (Non-appstore versions keep this under Documents/SimCity 4, I think.) I copied both the "Network Addon Mod" and the "z__NAM" folders in there.
Then I fired up SimCity, and all my sims suddenly had jobs. Yay!
After I got it working, I ran the installer a few times on the Windows side, each time copying over the resulting installations to Mac, so that I have a few different variations at the ready. This mostly worked, with some occasional wrinkles because I didn't have a SimCity installation on the Windows side. Usually I could just quit the installer and start over if it gave me trouble, and it worked the next time through.
Caveats
I've tried the other flavors of installation, and they cause SimCity 4 to crash when loading a city. After a very small bit of trial and error, some of the problem seems to be with something in z__NAM/Mass Transit Lots. I was able to get past loading when I removed that folder. Perhaps others with Mac experience (and a successful installation) can chime in with the parts that are/are not working in their configurations.
Closing
Thank You to everyone who has contributed to NAM and this forum, and also to Aspyr and those who worked on 64-bit and Catalina compatibility. It's good to see old games carry on. They're still fun.
