I’m going to repost this because its important for people to understand just how long Apple gave developers to migrate to 64bit.
Adobe, and many larger developers, were patently negligent when it came to coding for 64bit apps on the Mac. They had over a decade to compile for 64 bit, and move away from Carbon, and decided to do
nothing.
For the record, here’s the timeline for 64bit support on Mac OS X / macOS: (Taken from Ars Technica’s excellent macOS review)
- June 2003: The PowerPC G5 CPU is the first 64-bit-capable chip to show up in a Mac, and with Mac OS X 10.3 Panther, it can theoretically address up to 8GB of RAM.
- April 2005: Mac OS X 10.4 Tiger allows for 64-bit processes under the hood—they can be spun off from another process or run via the Terminal.
- June 2005: Apple announces that it will begin using Intel processors, which are still primarily 32-bit. Whoops!
- August 2006: Apple launches the Intel Mac Pro with a 64-bit Woodcrest CPU; mainstream 64-bit Core 2 Duo Macs follow shortly afterward.
- October 2007: Mac OS X 10.5 Leopard launches with actual support for regular 64-bit apps; Universal Binaries can run on 32-bit and 64-bit Intel and PowerPC machines, covering four architectures within a single app. Unlike Windows, Apple never ships separate 32- and 64-bit versions of Mac OS X.
- August 2009: Mac OS X 10.6 Snow Leopard still runs on 32-bit chips, but for the first time everything from the apps to the OS kernel supports 64-bit operation. Snow Leopard's 64-bit capabilities are a major component of Apple's marketing push, which infamously includes "no new features." However, most systems still default to loading the 32-bit kernel.
- July 2011: Mac OS X 10.7 Lion drops support for 32-bit Intel CPUs (Snow Leopard had already ended all support for PowerPC systems). Older Macs continue to default to the 32-bit kernel and 32-bit drivers, but new Macs introduced in this era typically default to the 64-bit kernel.
- July 2012: OS X 10.8 Mountain Lion boots into the 64-bit kernel by default on all systems that support it, including a few that previously defaulted to the 32-bit kernel. In the process, a few 64-bit systems with 32-bit graphics drivers and 32-bit EFIs are dropped from the support list.
- June 2017: Apple announces macOS 10.13 High Sierra and says it's the last release that will run 32-bit apps "without compromise."
- January 2018: All new apps submitted to the Mac App Store need to be 64-bit only.
- April 2018: High Sierra's 10.13.4 update begins warning users about "not optimized" (read: 32-bit) apps the first time they're launched.
- June 2018: All new apps and updates to existing apps submitted to the Mac App Store need to be 64-bit only. Apple announces macOS Mojave, which will be the last version of the OS to run 32-bit code.
- September 2018: Apple releases Mojave. 32-bit software continues to run but with more frequent and aggressive nag messages than High Sierra.
- June 2019: Apple announces macOS Catalina, which makes good on Apple's promise to drop 32-bit software support.
- October 2019: Catalina is released. 32-bit apps no longer run on the latest version of macOS.
Mojave will continue to receive OS security updates until the release of macOS 10.17, three years from now. Plenty of time to consider migrating to other options, or investing in an older Mac to continue to run your legacy software (which is what I have elected to do, see my sig below).
Now, in regards to stability, in my experience Catalina has been a little less stable in its initial release than 10.14 and no different from some of the earlier releases - 10.7 and 10.13 come to mind. If you’re worried about stability, then just wait for 10.15.1 or 10.15.2.