Delphi with FMX have supported OSX for many years.
You don't need the XLSZlibPas5.pas unit. It's used for some rare situations when Delphi's ZIP lib don't works. Just remove the unit. The gzip files is then not needed either.
I don't have a Linux installation so I can't test this but I can't see any reason why it not should work. Compiling for Mac which is a unix variant works. You will of course need the source code. You will also need Linux object files for gzip.
Hello I have put this on the todo list. As I have 300+ messages with you in my email thread with you, I consider you to have run out of support. 300+ messages is more than fair use. If you want more support then you have to purchase an upgrade of the component. You is of course welcome to report any...