The crash when opening saves on mac is definitely something to do with the threading, and i'd rather just test this first to see if it fixes it
Copied from my mod almost entirely as-is, with the changes to HTTP.cpp included, also added locks into Download.cpp even though it is probably overkill
you can get current OS / build information, exe name, restart tpt, open a link in the web browser, and use clipboard copy/paste functions
Also remove some older Platform.h file which wasn't really needed or used