[2021] Crash on Mac OS Catalina

No real ideas on this one, I have to say. The previous game CK2 is free to play on Steam now, does that have the same problem?

Please attach your Documents/Paradox Interactive/CK3/pdx_settings.txt .
From your Documents/Paradox Interactive/CK3/logs/ folder, attach system.log , error.log

Also in Steam please click on Steam-Help-System Info, and paste everything there into a text file and attach that here.  

I see nothing in those files to explain this; in Steam please click on Steam-Help-System Info, and paste everything there into a text file and attach that here.  

I'm afraid none of the game's hardware requirements on MacOS are met here:

• Processor: Intel® Core™ i7-7820HQ
• Memory: 12 GB RAM
• Graphics: AMD® Radeon™ PRO 560 (4 GB)

Unless you have Apple Bootcamp installed and can try the game under Windows, I suggest you seek a refund for this game from where you bought it.

Sorry about that!  

Updating the OS will not improve your hardware nor add more memory, I'm afraid.