I had the same. I changed the podfile to include these again:
# Workaround to prevent errors about missing unary_function in RCT_Folly
config.build_settings['GCC_PREPROCESSOR_DEFINITIONS'] ||= ['$(inherited)', '_LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION']
I reported it to Mendix, not sure whether this will be included in a template fix.
I also found a fix for my two remaining errors:
In your 'Linking Settings', at 'Other Linker Flags' add "-ld64"
Sources:
https://developer.apple.com/forums/thread/731089