Can Dimension be used on a closed network, i.e. one without an internet connection?

Hello!

As a general rule, All adobe apps will need an internet connection to install and then on a regular basis for checking if the billing info is correct
see info there:

https://helpx.adobe.com/uk/creative-cloud/kb/internet-connection-creative-cloud-apps.html

I don't know if anything applies to Dimension in particular

NOW:
I seem to remember that it is/was possible to buy the enterprise/team version of the software to use in a situation like yours (Government agencies, Cybersecurity companies, you see what I mean). That was possible by contacting Adobe directly.

Side note, as it may help, you can get links without the installer, see this blog post:

https://prodesigntools.com/creative-cloud-2023-direct-download-links.html
(By the way Prodesigntools is a legit company, a reseller of Adobe products, they have very informative blog posts.)

In any case the advice seems to contact Adobe directly, and they might advise you on the possibility (it's evidently restricted to particular situations and not just "I don't want internet on my computer" 🙂 You'll need a damn good reason)

If I find the official statement that it's possible, I'll post it here, in the meantime, to contact Adobe, go to Adobe.com (you'll be redirected to the country website you belong to), check the bottom right of your screen and click on the bubble speech you'll see there.
You'll get hooked with a chatbot at first, but ask to be directed to a real human and it should do.