How Update from Windows Server Essentials 2012R2 to Windows Server 2019

The two prerequisites to introducing the first 2019 or 2022 domain controller are that domain functional level needs to be 2008 or higher and older sysvol FRS replication needs to have been migrated to DFSR
https://techcommunity.microsoft.com/t5/Storage-at-Microsoft/Streamlined-Migration-of-FRS-to-DFSR-SYSVOL/ba-p/425405

I'd use dcdiag / repadmin tools to verify health correcting all errors found before starting any operations. Then stand up the new 2019 or 2022, patch it fully, license it, join existing domain, add active directory domain services, promote it also making it a GC (recommended), transfer FSMO roles over (optional), transfer pdc emulator role (optional), use dcdiag / repadmin tools to again verify health, when all is good you can decommission / demote old one.

--please don't forget to upvote and Accept as answer if the reply is helpful--

Upgrading from Server 2012 R2 to Server 2019 is supported as discussed here. I don't see any special cases mentioned for Essentials. The actual process is documented here.

However there are some things you should consider before going this route.

• If you do an inplace upgrade and something goes wrong along the way you are going to have to restore your original 2012 R2 server and software. You need to ensure you have a full backup of this system if at possible in advance. There is no way to test this in advance with an inplace upgrade.
• Your application(s) will be offline during the upgrade so ensure you can be down this long.
• Server 2012 R2 had lower system requirements than Server 2019. Your existing machine may not have sufficient resources to run the newer OS. Ensure your existing machine meets or exceeds all the system requirements. If it doesn't then you will need to get a new machine anyway.
• Unless you have Software Assurance (or the equivalent therein) then your Server 2012 R2 licenses won't work on Server 2019. You'll need to purchase updated server licenses. This may impact other things on the machine as well so ensure you have all the licenses you need before upgrading.