The SMG 10.9.0 Release Notes says "VMware ESXi/vSphere 7.0/8.0 are supported". Whereas, the SMG 10.9.0 Installation Guide says "ESXi/vSphere 6.0/6.5/6.7/7.0 server is supported (Recommended: ESXi Version 7.0 or later)". Which one is correct?
Release Notes is correct. Supported version of VMware ESXi/vSphere are 7.0/8.0.