Reading your article I have a few questions:

1 – You recommend the Hyper-V host to join a domain for security reaons. I assume you do not mean to join the host to your company network domain but make it a domain on its own for the purpose of extra functionality of a DC that makes it more secure?
I also read about joining your VMs to the host domain, obviously that would be a bad idea in my setup with external clients in my VMs but what could be a reason to do this?

2 – Is it not better/safer and more efficient to install just Hyper-V Server 2019 on the host? This way you do not have the vulnerabilities of Windows 2019 server on the host which should be managed, updated, rebooted, etc. You can connect with Hyper-v Manager to the host from any remote system to manage your VMs which makes Windows server on the host unnecessary to me.

• Security
• Convenience
• Feature availability
• Tool interoperability

Can you explain the reasoning for joining the host to the domain?

For small sites (under 25 users) I always build the raw host server, then install hyperv, then install domain services and create the domain on the host. Then I create a virtual server in hyperv and join that. In general I do fileserving off the host so that fileserving is not slowed by virtualization layers, and run application servers in vms. Note that the 2 vm licensing only applies to copies of windows server. So for example you can create a hyperv server, set the host as a DC, then set a virtual server as an application server for an accounting package, then set a second virtual server up with Ubuntu and run email on that. Also you can run as many workstation copies as you want as long as they are volume licensed copies and you have the proper number of licenses for them.

For larger sites I never put services (other than hyperv) on the server. I also never join the hyperv server to the domain and I do not run remote hyperv admin tools. All management of the vms is done by RDP into the hyperv server. It is safer that way because if the domain is compromised by an attacker who escalates to admin, you could literally have an antire network of servers, all vm’s, cryptolocked or destroyed and the hypervisor would not be touched and you could restore all of those from image backups.

I get that there’s a lot of management tools out there that hate this but with hypervising you need to start thinking about your hyperv servers as completely separate from the network the guests use. If you built your servers in the cloud under Azure you wouldn’t have access to the hyperv server either that Microsoft runs them on. The less access anyone has to the hyperv server the safer.

You have to install guest operating systems separately.
An OEM license should grant you the normal virtualization rights in theory. Each OEM can modify the terms of the license, though. I do not have the details on how to use OEM keys in a virtual machine. Contact the sales team of the company that sold it to you and see if they have a licensing expert on staff that can answer that question. Support almost never knows.

No, it won’t activate automatically. I do not know the details of the keys that came with your purchase. Call your Dell sales rep and ask them to connect you with a licensing expert.

1 – Yes
2 – A physical host fully licensed for Windows Server 2019 Standard Edition can run two virtualized instances of Windows Server 2019 Standard Edition. If you run any software in the management operating system for any purpose other than managing the local system and its virtual machines, then you forfeit the right to run one of those two instances. Please contact your Microsoft licensing reseller for details as I am not a lawyer and I am not credentialed to provide licensing advice.