In-Place Upgrade WIndows Server 2012 R2 Standard to 2019 Error

In order to perform an in-place upgrade you'll need to run setup.exe from the root of the install media within windows. The media needs to be licensed retail or volume, not evaluation. That being said an in-place upgrade is never recommended and a very risky move. The better option is to build a new one from scratch.

The two prerequisites to introducing the first 2019 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. Then stand up the new 2019, 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.