Apple has been very difficult to develop software for over the years. They keep pulling out the rug from underneath me with their frequent hardware and OS changes.
I develop for both Mac and Windows. The only change I had to make for Windows was many years ago in the transition from 32 to 64-bit.
With Mac, here is the list of major revisions I have had to make to get my software to run. The amount of time involved in each ranges from weeks to 2 years (#6). And most of these required me to buy new Macs to use for development and testing.
1) Mac OS 9 to OS X
2) Motorola 680X0 to PowerPC
3) PowerPC to Intel
4) 32-bit to 64-bit
5) Intel to Apple M1 chip
6) Mac OS X to Big Sur and Monterey - major changes to the way programs draw to the screen and numerous 'Deprecated' functions - functions which have been deleted (or soon will be) from MacOS
My customers blindly 'upgrade' to the latest version of MacOS, oblivious to the implications it will have with their existing software.
MacOS Catalina, Big Sur, and Monterey broke my program. I spent 2 years rewriting it. Today, for example, I got a call from a customer who complained that my program doesn't work on his latest version of MacOS.
I explained to him that it requires a new version of my program because of the changes Apple made and he said "you mean I have to shell out $99 to use the software on the latest MacOS". I calmly replied "Well at least you didn't have to spend 2 years of your life making the required changes to the program like I did". He was speechless.