Kindly confirm if this SQL Query MP supports SCOM 2019.
Also could you please share us the details how to enable this monitor.
Do you mean this one:
If so, then I believe it was developed on SCOM 2016 and will work on 2019.
Based on my testing it works fine in SCOM 2019 but does require the legacy SQL management packs to discover the databases for the query wizard. A new version will be required to use the database discovery from the universal SQL MP, not sure if that’s in development. It is one of the main reasons we have held off on migrating to the new SQL MPs.