just a heads-up for you guys:
This is from a recording I got from a client, who run in the trap.
FileMaker 19.4 needs macOS 10.15 or newer because of the objc_opt_self function not present in older macOS version.
If you try to run FMP 19.4 on older macOS, you will get a crash with the function missing.
Same here when you try to use the iOS SDK on newer macOS.