I've installed the latest releases of FPC and Lazarus and I followed the instructions I found at
https://wiki.lazarus.freepascal.org/Cocoa_Interface to compile my mac app to run on as a 64-bit app:
Open your project with Lazarus and click Project/Project Options
In the "Config and Target" panel set the "Target CPU family" to be "x86_64"
In the "Additions and Overrides" panel click on "Set LCLWidgetType" pulldown and set the value to "Cocoa"
In the past, for some reason Lazarus kept setting the compiler to "/usr/local/bin/ppc386" - which results in 32 bit apps. Make sure under Tools->Options that "Compiler Executable" is set to "/usr/local/bin/fpc" to get 64 bit apps.
Now compile your project - with any luck it will work OK.
However, I keep getting this compiler message: "cocoarichmemo.pas(16,30) Error: Identifier not found "TCocoaTextView"
So it won't compile the unit CocoaRichMemo. It seems like I'm missing a path in my configuration but I'm at a loss (forgive me, I'm a mostly PC guy so this is a bit of a challenge)