I have tested and implemented an
Apple supported solution today in 2020 to continue playing Company of Heroes I for those who previously purchased the stand alone download through the App Store (NOT Steam), now that 32-bit support has ended with the introduction of OS X Catalina (10.15). The answer is basically to create a volume on the disk (NOT a separate partition) and install an earlier OS X such as Mojave on that volume. Now, my laptop always boots to Catalina as always, but if I want to play COH-1, I hold the option key when turning on and the laptop and it boots to Mojave. Boom! Play COH-1 same as before. Initially, I thought the steps were intimidating, but found the process rather straight-forward in hindsight. There was no code or command prompts involved. It's strictly common user interface level steps. This process can works for Mojave or other recent versions of OS X. I Summarize the steps as follows:
1) Review MacWorld article on Dual Booting to understand general process:
https://www.macworld.com/article/3284378/how-to-create-a-bootable-macos-mojave-installer-drive.html.
2) Use Time Machine in OS X Catalina System Preferences to create a full system backup (or update your current backup). This is always a standard best practice to undo changes.
3) Obtain at 16GB USB keychain drive.
4) Download and Install "Disk Creator" software as described in article.
5) In Catalina, download OS X Mojave from App Store. Use links in MacWorld article if necessary to get the Mojave install file. NOTE: Make sure you decline the installation which is prompted right after the download completes. Cancel out!
6) Using "Disk Creator", make a USB Startup Disk that can install Mojave later on.
7) In Catalina, open "Disk Utility" app. Create a new Volume (not a partition) (I called my new volume "Mojave"). 30-40GB max size should be sufficient, however if you have other 32-bit apps you want to use, you may want a higher max. I did not state a reserved amount. (One particular benefit is that the AFHS format allows available space to be shared with the Catalina drive while still keeping the Mojave volume data and operation completely separate. So making 40GB max does not mean Catalina can't use it if you run out of space. (If you create a Partition instead of a Volume, this would not be allowed.) Volumes are a relative recent feature introduced by Apple to work with drives formatted AFHS.
8)Shutdown then turn on machine with USB plugged into Mac and HOLD "OPTION" key as it reboots.
9) At prompt, Select USB drive to start up with and not the internal drive.
10) As the USB starts, select to begin the Mojave Installation. In the next steps, make sure you select the New Volume as the destination when prompted, not the Catalina drive. Installation will begin. System will restart when done.
11) System should boot to Catalina normally. In System Preferences, there is an item called Startup Disk. You can choose which OS X you want to boot up to automatically upon turning on your computer. Mine is set to Catalina so my wife can use the Mac none the wiser.
12) Shut down from Catalina
12) Turn on mac and immediately hold down the OPTION key. The Mac should prompt you to select which drive to boot from. At the prompt, select your drive with Mojave on it. Computer will boot to Mojave volume. I skipped all iCloud and setup steps.
12) Now that you are in Mojave, sign into App Store after reaching desktop. Go to Purchased Apps. Download a fresh copy of COH-1. (This will only work if you bought COH-1 before it was taken off the App Store. It is no longer available for purchase, only download for current owners.)
13) Reboot computer without holding OPTION key. Mac should boot normally to Catalina.
I have been playing for several nights now. No Issues!!!!! And best of all Apple supported!!!!
