Opmantek has released a new NMIS8 Virtual Appliance Release; it may be downloaded here:
https://dl-nmis.opmantek.com/Opmantek-20200708-VM8-Centos7.2003-64bit.ova

Release notes:  Opmantek NMIS8 Virtual Appliance: Release Notes

Installation & Getting Started:  Opmantek Virtual Appliance: Installation and Getting Started