In this article, I added four videos covering the complete steps required to remove the Exchange server in a hybrid environment. Exchange Server needs to be appropriately uninstalled from a Hybrid Environment, and the decision depends on some factors.
The following videos explain all the possible scenarios and a step by step demo.
Microsoft Documentation: https://docs.microsoft.com/en-us/exchange/decommission-on-premises-exchange
Video 1: How to decommission On-premises Exchange Server in a Hybrid Setup
Video 2: Remove Hybrid Configuration
Video 3: Remove Directory Synchronization
Video 4: Remove Exchange Server