As of the Office 2019 version, Microsoft no longer makes any ISO data carriers available. You need to generate these yourself accordingly as follows:

Download only via Deployment Tool:
Access the tool directly here

Create the configuration file in an .xlm format relatively simply at  https://config.office.com/ 

Microsoft has implemented an extremely inconvenient solution with the new click-to-run installer for Office 2019, which imposes extra work on the IT service provider or end customer.
Here in advance, the official installation instructions from Microsoft.

The correct implementation of the Office Deployment Tool (setup.exe) and to trigger the corresponding download in the Microsoft CMD network, the setup.exe file must not be opened by double-clicking, but implemented via the Windows command line.

Start → Execute cmd
Please switch in the prompt in the folder in which the setup file and the configuration.xml are located using CD (e.g. CD E: — CD \Temp\Office Deployment Tool).
In this folder, please execute the command Setup/Download configuration.xml, which starts a download of the respective installation files.
Explorer shows you then, that a new folder has been created into which the installation files are downloaded.