Hello Alex T⚜️ 

I would like to know how to do it this way:
Production instance: production(.)com and

Testing instance:  testing.production(.)com

What do we need to change after rsyncing (copying) production to subdomain testing.production(.)com?

Where to change the testing URL and what else do we need to change so that the testing.production(.)com will work? What about DB (we are using MySQL - Ubuntu 20.04 LTS LAMP server )?

Thank you.

Mayki