The new separate test environment server would be also windows 2019 server? I am assuming that you will be using 2019 server.
You will need two windows 2019 server. One for Application and one for Database.
For application, Install websphere manually, setup cluster as per your requirement like having different JVM (UI, MEA, CRON, REPORT) clusters or just MXServer, since it is Test environment.
Setup queues configuration. Complete the WAS Setup. Now go inside SMP folder in prod, Update maximo.properties with tnew test db server string. Then build EAR file and deploy the same on new test application server.
For Database, Install Microsoft SQL Server 2019, then take the DB backup from Prod one and restore it on your new test server.
Change some system properties, since it is production db like smtp property, disabling integration. so it does not impact end-users.
Hope this helps.