Hello Nick,
I am not sure you can do this with the Essentials SKU. Back in the days with 2012/2016 Essentials you can not deploy 2 Essentials servers and have one as a member server because the Essentials SKU must be configured as Domain Controller and they must hold all FSMO roles.
With 2019 it is confusing. From here Windows Server 2019 Essentials update - Windows Server Blog
Windows Server 2019 Essentials has the same licensing and technical characteristics as its predecessor, Windows Server 2016 Essentials. If configured as a Domain Controller, Windows Server 2019 Essentials must be the only Domain Controller, must run all Flexible Single Master Operations (FSMO) roles, and cannot have two-way trusts with other Active Directory domains.
The second sentence above makes me wonder. 'If configured as a Domain Controller'.... on 2016 you must have the Essentials Server configured as a DC but this sentence makes me believe 2019 does not have this limitation... but but but. I don't know.
If I read this then you should not be able to do what you want to do. As a matter of fact I would not do what you suggest, I would go for Standard and virtualize the two workloads as Viirtual Machines on the Hyper-V Host. The two VM's will be Windows Server 2019 Standard and one them is the DC and the other one holds the SQL server.
Hope this helped.
answered 02/22/2019 15:32