Disable the node so that no new VMs will be scheduled on this host. Instructions: Disable a compute node howto
Migrate the instances on this compute node to other hypervisors. Instructions: Migrate an instance howto
Reinstall the host with CentOS8 using Foreman. Move the host to the 'hosts_all' hostgroup
Make sure that SElinux is disabled
[root@cld-np-19 ~]# getenforce Disabled
Install OpenManage, if this is a DELL host. Instructions: OpenManage howto
Configure the management and data network
Stop puppet: