Tom Collins has a checklist of things to consider before upgrading to SQL Server 2019:
Application Lifecycle – Each SQL Server version gets 10 years support. 5 years in mainstream support & 5 years in extended support
Mainstream support includes functional, performance, scalability and security updates.
Extended support includes only security updates.Analyse these support levels in the context of your organisations requirements . If the organization has a large footprint with a large multi-year upgrade cycle – than that will have different considerations to smaller scale
Read on for the full list.