BT Directory Sync Pro for AD system requirements supports up to SQL Server 2017. According to the MS support page, the mainstream support for SQL Server 2017 will end in October 2022.
SQL Server 2019 is supported today. BT Directory Sync Pro for AD 20.11.0 released Dec 2021 is the first release that was certified to work with SQL 2019. The documentation will be updated in the next product update.