A family of System Center products that provide infrastructure monitoring, help ensure the predictable performance and availability of vital applications, and offer comprehensive monitoring for datacenters and cloud, both private and public.
No, there is no supported way of "attaching a database from one environment to another", regardless of their version. Neither have I ever seen it documented anywhere.
Once again, the only supported way to keep your data is to keep your current SCOM 2012 deployment and upgrade it to SCOM 2019.
You can do that and update your environment to Windows 2019/SQL 2019 in the meantime, but that will require a bit of planification...