Is there support for a BigFix agent v10.x on FreeBSD v11.4?
No, FreeBSD is not currently supported. Here you can find the official support matrix: https://support.hcltechsw.com/csm?id=kb_article&sysparm_article=KB0087327
There is a RFE already opened; you can vote and monitor it: https://bigfix-ideas.hcltechsw.com/ideas/BFP-I-91
Regards.