The documentation for installing the WebSphere Application Server Developer Tools into eclipse mentions an option for installing files without an internet connection.

However, I cannot find the location to download the zip file in the provided links. How can I get the files for an offline installation of the WDT?

Here is the link I have referenced:

https://www.ibm.com/docs/wasdtfe?topic=eclipse-installing-updating-into-existing-workbench

WDT installation files are available as zips from DHE here:

https://public.dhe.ibm.com/ibmdl/export/pub/software/websphere/wasdev/downloads/wdt/

Please choose the directory that matches the level of Eclipse that you will be installing, and download the highest level of wdt-update-site available.

For your information, here is the list of Eclipse Releases:

https://www.eclipse.org/downloads/packages/release

Please transfer that zip to your target machine, then install it into your Eclipse using the instructions at:

https://www.ibm.com/support/knowledgecenter/SSHR6W/com.ibm.websphere.wdt.doc/topics/t_install_wdt_eclipse.html#installingfromdownloadedinstallationfiles

Note that active support will only be offered for installations on Eclipse 2020-03 or newer. (as of 2021 Apr.)

Thus, you can install the downloaded installation files while not connected to the internet.

I recommend unchecking the button "Contact all update sites during install to find required software" under “Available Software".