Microsoft frequently releases Cumulative Updates (CUs), which are full 64-bit installers. You do not need to install the original RTM version first; you can perform a clean installation directly using the latest CU ISO. Download Cumulative Update 15 (CU15) . Download Cumulative Update 14 (CU14) .
Once the ISO is downloaded and the server is ready, the administrator mounts the image. But the installation doesn't start with a "Next" button; it starts in the Command Prompt to prepare the kingdom—Active Directory. How can I download the Exchange 2019 ISO? - Microsoft Learn
Verify the SHA-1 hash from Microsoft. Use Get-FileHash in PowerShell. Redownload if mismatch.
Before the ISO is even mounted, the administrator must ensure the "environment" is hospitable. Exchange 2019 is a resource-intensive beast with strict requirements: : A minimum of 128 GB of RAM