Transfer iCloud content of someone who has passed away.

So are you talking about on a computer? iCloud has different components and how you get access to them depends upon the feature you are using. The Photos app handles photographs, Contact handles contacts, etc. All things are synced to the equivalent app on a computer so if you have a user directory on a computer signed into iCloud and the feature is active, all the files should also be on the computer.

E.g., Use iCloud Drive to store documents on your Mac, iPhone, and iPad - https://support.apple.com/guide/mac-help/store-files-in-icloud-drive-mchle5a61431/mac

This article explains how:

How to request access to a deceased family member's Apple accounts - https://support.apple.com/HT208510