Hi @williamotto
I’m not 100% sure, but I believe that ACF will only load the field groups from the individual site. This means it is not possible to make a ‘master’ field group.
That said, I have a feeling if you used the ‘export to PHP’ feature in ACF and saved the field group data to a separate file, you could get all your multi-sites to load in that file, therefore creating the same field groups across all sites.
Does that help?
Thanks
E