Not built yet — honestly. Here is what this page will offer once it is.
Everything the normal install fetches from the internet, prepared as a set of files sized to CDs/DVDs or USB sticks (several disks — the payload is bigger than one). You will download each disk's file list on a connected computer, write the files to the media, and install on the offline machine from those — no connection needed there, ever.
The pieces can be generated one at a time straight onto the medium, so even the server never needs the whole set on disk at once.
A copy of everything the installer would normally fetch from the internet, prepared onto CDs/DVDs or USB sticks — so a computer with no connection at all can still install the suite. You download the pieces somewhere WITH internet, write them to the media, and carry them over.
The full offline payload is bigger than one disk, so it is split into chunks sized to your media. Each chunk below lists exactly which files belong on it and how big they are — copy each list onto its own disk or stick, label them, and the installer asks for them in order.
Honestly: the signing story for offline media is still being decided (it is an open design decision, not an oversight). Until it lands, download only from an instance you trust and keep the media under your control. This answer will change when the verification design ships.