In Exchange 2019, like Exchange 2010/2013 and 2016, you can move your active mailbox databases to another server using the scripts that come with your Exchange Installation.
They are located in the V14\Scripts or V15\Scripts folder depending on your version you have installed.
To move a database, you can simply run the following command:
- Move-ActiveMailboxDatabase -Server exchange-2016 -ActivateOn
- Server exchange-2019 -Confirm:$all
In this example the database in question is not redundant but it should give you a succeed/successful response once complete.
Hope it helps.