Can we use sql server 2016 with service pack 2 for SharePoint 2019?
As a short answer, Yes SharePoint 2019 supports SQL Server 2016 with SP2.
The Minimum requirements for a database server in a farm One of the following:
Microsoft SQL Server 2016 RTM Standard or Enterprise Editions
Microsoft SQL Server 2017 RTM Standard or Enterprise Editions for Windows
Note: SQL Server products and all future public updates are supported through the SQL Server product lifecycle that means SQL Server 2016 with SP2 is supported.