Hi Rich, I'm sorry to say that Windows Server 2019 is not a supported platform at this time however Win 10 is supported.
Immunet does have an "enterprise version" that I believe will work with Windows Server 2019 called AMP for Endpoints (AMP is an acronym for Advanced Malware Protection).
It's not free but the price is reasonable and actually negotiable depending on the length of your license that you choose and the number of endpoints to be protected. Plus you get much better malware/intrusion protection compared to Immunet in a server environment.
So take a look to see it AMP for Endpoints better meets your needs. https://www.cisco.com/c/en/us/products/security/amp-for-endpoints/index.html