BigFix agent v10.0.6 worked successfully on Amazon Linux 2018 (based off RHEL6) even though it was not supported by HCL.
Trying 10.0.8 BigFix agent x86_64 on AL 2018 fails due to /etc/init.d/besclient calling systemctl which does not exist on AL2018. There is a comment at the top of the init script saying it was auto generated and it is interesting that on RHEL6, the init.d script works as expected and is very different then the AL2018 version.
https://bigfix-ideas.hcltechsw.com/ideas/BFLCM-I-188 has been created for HCL to officially support AL2018.