The simplest / safest solution is to seize roles to another healthy one
seize FSMO roles in Active Directory Domain Services
then perform cleanup to remove remnants of failed one from active directory
Clean up Active Directory Domain Controller server metadata
Step-By-Step: Manually Removing A Domain Controller Server
then stand up a new one for replacement, I'd use dcdiag / repadmin tools to verify health correcting all errors found
before starting any
operations. 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.
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