Hello Murray,
As you suggested, I added a .hostname file and ran ./simfactory/bin/sim build --clean --reconfig . I'm past the -fopenmp issue which plagued me for days! Thank you.
Glad to have been able to help.
While I was trying to get around the -fopenmp problem, I edited the file /Users/murray/Cactus/configs/sim/OptionList . I'm not sure if that file is input or output. It's input, but it might be both. I changed the version name (added a '_' at the end of the version string); set the compiler and preprocessor directives to use gcc-10, etc.; and turned the OpenMP options off.
The file is both. When you ran ./simfactory/bin/sim setup-silent then simfactory created a custom option list named generic-10.cfg or so in simfactory/mdb/optionlists/ and a custom machine ini file pointing to that option list in simfactory/mdb/machines/. When you then ran simfactory/bin/sim build it copied that option list to OptionList and used it with Cactus to compile the code. Cactus then generates an almost copy of that file in configs/sim/config-info and eventually a makefile fragment based on that information in configs/sim/config-data/make.config.defn.
Yours, Roland